East Sussex on Wikipedia.

Alciston. The dedication is lost. TQ 5058 0556. From an old postcard in Geoff Watt's Collection. Link. Grade I listed.
Alfriston, St. Andrew. From an old postcard in Steve Bulman's Collection. A modern view. © Graeme Wall. Link.

Battle.
Beckley, All Saints. TQ 843 237. From a postcard in the Kevin Gordon Collection. Link.
Beddingham, St. Andrew. TQ 445 079. © Kevin Gordon. Link.
Bexhill, St. Mary Magdalene. From an old postcard in Steve Bulman's Collection. The card was posted in 1957, but is evidently much older.
Bishopstone, St. Andrew. It contains much of Saxon date including the south porch. A 12th century tomb slab, and the font. TQ 4724 0098. All © Christopher Skottowe (1963). Link1. Link2. The (very brief) grade I listing.
Blackboys, Hope Strict Baptist Chapel. Another view, and two interiors - 1, 2. All © Gerard Charmley (2016).
Bodiam, St. Giles on Levetts Lane. Originally a chapelry to St. James the Great at Ewhurst, most of the fabric appears to be C13, though there may be earlier work. Another view. TQ 7824 2619. Both © Carole Sage (2016). Link. A good history here. Grade II* listed.
Brede, St. George on Brede Hill. Another view, two interiors - 1, 2, the pulpit and font. A fine tomb is the resting place of Sir Goddard Oxenbridge, reputedly 7 foot tall, and hence the "Brede Giant". Two windows - 1, 2, the latter of St. George. TQ 82532 18266. All © Carole Sage (2016). Link. A good history here. Grade I listed.
Brightling, St. Thomas a Becket. The pyramid is the tomb of the one-time MP "Mad Jack" Fuller. TQ 683 210. From a postcard in the Kevin Gordon Collection. Link.
Brighton.
Burwash, St. Bartholomew. Of Norman foundation, the tower dates from C12, the rest of the church is largely C13, but it was partly re-built and "restored" in the 19th. This was the parish church of the Kipling family, and there is a plaque to Rudyard's son, killed in WW1. Another view. TQ 67715 24748. Both © Carole Sage (2016). Link1. Link2. Grade II listed.
Burwash Weald, St. Philip. Two additional views - 1, 2, two interiors - 1, 2, the pulpit and font. TQ 63983 23652. All © Carole Sage (2016). Link1. Link2.
Buxted, St. Margaret the Queen. From an old postcard in Peter Wenham's Collection. A modern view, © Peter Wenham. Link.

Chailey, Free Church. © Geoff Watt.
Crowhurst, St. George. From an old postcard in Steve Bulman's Collection. Link1. Link2.

Dallington, St. Giles. © Chris Emms (2011). An interior view, from an old postcard in Judy Flynn's Collection. Grade II* listed - link. Former Methodist Chapel - has been disused for several decades. © Chris Emms (2011).
Denton, St. Leonard. Interior view. TQ 454 025. Both © Kevin Gordon. Link.
Ditchling.

Eastbourne.
Etchingham, The Assumption of Blessed Mary and St. Nicholas. A C14 church on an earlier site, it was at one time surrounded by a moat. A further two views - 1, 2. TQ 71363 26206. All © Carole Sage (2016). Link1. Link2. Grade I listed.
Ewhurst Green, St. James the Great, largely of the C12 and C14. Three more views - 1, 2, 3. TQ 7956 2457. All © Carole Sage (2016). Link. The very brief Grade I listing.

Fletching, St. Andrew and St. Mary the Virgin. © Chris Emms (2011). Link. Grade I listed - link. 
Folkington, St. Peter. TQ 559 038. © Kevin Gordon.
Framfield, St. Thomas à Becket. © Peter Wenham. Interior view, © Gerard Charmley (2016). Link.
Frant, from an old postcard, Steve Bulman's Collection.
Friston, St. Mary the Virgin. TV 552 982. Kevin says the church is now surrounded by trees. From a postcard in the Kevin Gordon Collection. A modern view is available here. Link.

Glynde, St. Mary the Virgin. TQ 457 093. © Kevin Gordon. Link.
Groombridge, St. Thomas the Apostle. Link. St. John. Both from an old postcards, Geoff Watt's Collection.
Guestling, St. Laurence on Church Lane. Another view, the lich-gate, and its memorial plaque. TQ 85566 14479. All © Carole Sage (2016). Link. Grade I listed (tower only, which is Norman).

Hampden Park, St. Mary. Link. St. Joachim (R.C.). Both © Graeme Harvey.
Hastings.
Herstmonceux, All Saints. TQ 643 102. © Kevin Gordon. Link.
Hooe, St. Oswald. Another view, and the sun-dial. All © Steve Bulman (2009). Link.
Hove.

Icklesham, St. Nicholas. © Geoff Watt. Link.
Iden, All Saints, Norman, with C15 work. Another view, and two interiors - 1, 2. TQ 91551 23752. All © Carole Sage (2016). Link. Grade I listed.
Iford, St. Nicholas. TQ 408 074. From a postcard in the Kevin Gordon Collection. Link.

Jevington, St. Andrew. From an old postcard (franked 1904) in Steve Bulman's Collection. Link.

Kingston, St. Pancras. © Graham Parks (2012). Link. Grade II* listed - link.

Lewes.
Litlington, St. Michael the Archangel (O). Curiously, Pevsner fails to give the dedication. TQ 523 019. © Dave Westrap. An old postcard view, from Reg Dosell's Collection. Another view, two interior view - 1, 2 - and the font, all © Steve Bulman (2009). Another view, © Elaine Saunders (2016). Link.
Lullington, Church of the Good Shepherd. One of the smallest churches in Britain, though only the remaining portion of a once larger church. TQ 588 031. From an old postcard in Steve Bulman's Collection. Two modern views - 1, 2, and the interior, all © Carole Sage (2016). Link1. Link2. The very brief Grade I listing.

Maresfield, St. Bartholomew. From an old postcard in Steve Bulman's Collection. Link.
Mayfield, St. Dunstan (O). TQ 5865 2703. From an old postcard in Steve Bulman's Collection. Interior view, and an iron tomb slab - note the reversed "7" and the "N" towards the top. © Judith Anderson (2009). Three further views - 1, 2, 3, all © Elaine Sanders (2016). Two more interior views - 1, 2, a monument, and the font, all © Karel Kuča (2007). Link. Grade I listed. Numerous tombs and headstones are listed separately - they can be seen here. Baptist Chapel on West Street and South Street. TQ 5849 2690. © Judith Anderson (2009). Link. Colkins Mill Church (Evangelical, previously Congregational) on Station Road. According to its Genuki entry it was originally Bible Christian, founded in 1825. TQ 5833 2696. © Judith Anderson (2009). Link. St. Thomas of Canterbury (R.C.) on Station Road, as seen by Streetview in 2019. TQ 5814 2690. Link. St. Mary and the Angels (R.C.) on St. Mary in the Fields, at TQ 5854 2683. It's shown on maps from 1931 to 1976, the latest available to me. Streetmap hasn't visited, so I don't know if it survives, and I haven't been able to find a photo of it.
Mountfield, All Saints, mostly C12, with a slightly later tower. Two additional views - 1, 2, and the porch. TQ 7348 2028. All © Carole Sage (2016). Link. Grade II* listed.

Newhaven, St. Michael. TQ 442 011. From a postcard in the Kevin Gordon Collection. Link. Christ Church, which stood on South Road, was demolished in 1969. From a photo in the Kevin Gordon Collection.
Newick, St. Mary. From an old postcard (franked 1911) in Steve Bulman's Collection. Link.
Northiam, St. Mary. Another view. TQ 830 245. Link. Northiam Unitarian Chapel, identified by Janet Gimber. TQ 823 250. All © Steve Bulman (2009).

Offham, St. Peter. TQ 401 122. From a postcard in the Kevin Gordon Collection. Link.

Peasmarsh, St. Peter and St. Paul on Church Lane. © Bill McKenzie. Two additional views - 1, 2, two interiors - 1, 2, a window, the pulpit and the font, all © Carole Sage (2016). Link. Grade I listed. Former chapel (now a private residence), © Geoff Watt. Janet Gimber advises that this was Wesleyan Methodist.
Penhurst, St. Michael the Archangel, on Penhurst Lane. Another view, and the porch. TQ 6943 1656. All © Carole Sage (2016). Link1. Link2. Grade I listed.
Pett, St. Mary and St. Peter (1864). TQ 8729 1391. From an old postcard, in Reg Dosell's Collection. A modern view, © Carole Sage (2016). Link1. Link2. Methodist Church (1848). Two further views - 1, 2. TQ 86987 13937. All © Carole Sage (2016). Grade II listed.
Pevensey, St. Nicholas. From an old postcard in Steve Bulman's Collection. Another old postcard view, this one from Reg Dosell's Collection. A modern view, © Stuart Mackrell. Grade I listed.
Piddinghoe, St. John the Evangelist. From an old postcard in Paul E. Barnett's Collection. Link. Grade I listed.
Playden, St. Michael on Rectory Lane, which dates from the late C12. Two further views - 1, 2, and the interior. TQ 9202 2168. All © Carole Sage (2016). Link. Grade I listed.
Polegate, from an old postcard, Steve Bulman's Collection. U.R.C., formerly the Congregational Church. TQ 584  050. From a postcard in the Kevin Gordon Collection (posted 1907). Link.

Ringmer, St. Mary the Virgin. TQ 445 126. © Kevin Gordon. Link.
Ripe, St. Andrew. © Chris Emms (2011).
Robertsbridge, U.R.C., originally Congregational (1881), which Pevsner records, rather unkindly, as "truly horrible". Bethel Chapel (1842). Both © Steve Bulman (2009). Darvell Bruderhof, © Alan K. Taylor. Link.
Rotherfield, St. Denys. From an old postcard (ca. 1910), Brett Jeffrey's Collection. One of Judy Flynn's old postcards was previously in the Unknown section - it was posted from Tunbridge Wells to Boscombe in 1905, and written on the back is "This photo was taken the day after our harvest thanksgiving." Interiors are always difficult to identify, so my thanks to Simon Davies for identifying this, and supplying the following confirmatory link. A modern view, the interior, pulpit and tester and the font, all © Elaine Sanders (2016). Justin Brice has told me that the church was burgled some years ago. One item stolen was a 1711 painting of an old windmill by Humphrey Fowle. As part of his researches into this mill, Justin is keen to find a photograph of this painting. Can you oblige? Link. Grade I listed.
Rottingdean, St. Margaret. From an old postcard (franked 1904), Steve Bulman's Collection.
Rye.
Rye Harbour, Church of the Holy Spirit (CoE). Memorial to Lifeboat men. TQ 937 190. Both © Dave Westrap. Another view. © Steve Bulman (2009). An old postcard view, from Kevin Gordon's Collection. Link. Church Mission Room. Approx. TQ 940 190. © Steve Bulman (2009).

St. Leonards-on-Sea, Christ Church. From an old postcard (franked 1906), Steve Bulman's Collection. St. Ethelburga, built in 1929. From a postcard in the Kevin Gordon Collection. Link.
Salehurst, St. Mary the Virgin. Another view. Both © Steve Bulman (2009). Another view, the interior and font. The font was gift from Richard I, in appreciation of the local abbot's involvement in the negotiations for his release from captivity. All © Elaine Sanders (2016). Link.
Seaford.
Sedlescombe, St. John the Baptist (O). Interior view, and an angel. TQ 776 188. All © Steve Bulman (2009). Link.
Southease, St. Peter. The re-dedication is modern, as the medieval one was lost. TQ 423 053. From a postcard in Kevin Gordon's Collection. A modern view, and an interior view, both © Chris Emms (2011). Link. Grade I listed.
Stanmer, no dedication (CoE). © Bernard Hylands. Link.
Staplecross, St. Mark. © Steve Bulman (2009). Link.
Streat, Parish Church (dedication unknown). © Graham Parks (2012). Link. Grade II* listed - link.

Tarring Neville, St. Mary TQ 444 038. © Kevin Gordon. An old postcard view (card franked 1905), from Steve Bulman's Collection.
Ticehurst, St. Mary the Virgin on Church Street is largely of C14, but there is some fabric from the preceding century. From an old postcard in Steve Bulman's Collection. Two modern views - 1, 2, the pulpit, font and East window, all © Elaine Saunders (2016). Another view (showing the recently added St. Mary's Room), and two interiors - 1, 2, all © Carole Sage (2016). Link. Grade II* listed.

Upper Dicker, Holy Trinity. TQ 553 099. From a postcard in the Kevin Gordon Collection. Compare with this modern view (and another) - note that the triangular hat on the bell cote has gone. © Steve Bulman (2009).

Wadhurst, St. Peter and St. Paul. From an old postcard, Geoff Watt's Collection. A modern view, the interior, and the font, all © Elaine Sanders (2016). Grade I listed. The former Methodist Church, built as Wesleyan in 1874. It is presently for sale. © Elaine Sanders (2016).
Waldron, All Saints. From an old postcard in Steve Bulman's Collection. Another view, from a postcard in the Kevin Gordon Collection. Kevin advises that this church is also known as All Hallows. TQ 549 193.
Wartling, St. Mary Magdalene. TQ 658 092. From a postcard in the Kevin Gordon Collection. Link.
West Dean, All Saints. TV 525 996. © Dave Westrap. Link.
Westham, St. Mary, situated beneath the walls of Pevensey Castle. TQ 642 046. From a postcard in the Kevin Gordon Collection, and another from Reg Dosell's Collection. Link.
Whatlington, St. Mary Magdalene. Another view. Both © Steve Bulman (2009). Link.
Willingdon, St. Mary the Virgin. From an old postcard in Steve Bulman's Collection. Link.
Wilmingon, St. Mary and St. Peter. Founded circa 1000 A.D., the first church was replaced by the present one in the twelfth century, the chancel of which served as the church for the monks of the priory. Two further views - 1, 2, the interior, altar, pulpit and tester, and the font. The modern window by Paul San Casciani incorporates some glass from one destroyed in a fire in 2002, as well as a phoenix rising from the ashes. He also designed the Millenium window. An early and rather crude carving is built into the chancel wall. Removed here from the outside wall of the church, it has been plausibly suggested that it represents the Madonna and child, but see also link1. The churchyard has a famous old yew tree, claimed to be over 1500 years old. TQ 54414 04281. Link1. Link2. The very brief grade I listing. The remains of the priory (C12). TQ 54382 04257. Grade I listed. All © Carole Sage (2016).
Winchelsea, St. Thomas the Martyr. From an old postcard, Steve Bulman's Collection. Three modern views- 1, 2, 3 - all © Steve Bulman (2009). Link. Wesley's Chapel (Methodist). Winchelsea was the last place that John Wesley delivered a sermon, beneath a large ash tree, beside the old church. © Steve Bulman (2009).
Winchelsea Beach, St. Richard of Chichester (1935). Another view. The "Rhenish Helm" roof is unusual - see also Sompting in West Sussex. Both © Steve Bulman (2009).
Withyham, St. Michael and All Angels. From an old postcard, Steve Bulman's Collection. Link.
Wych Cross. At first glance this church looks a bit like Whippingham on the Isle of Wight, but it isn't. Diana Bond had asked for  help in identifying it. Paul Smith has advised that Wych Cross Church, which was dedicated to St. Richard de Wych, although never consecrated, was built in 1866 and demolished in 1975.