Vale of Glamorgan on Wikipedia.

Barry and Barry Island.
Bonvilston, St. Mary the Virgin (CiW). Zoar Presbyterian Church. Both © Gerard Charmley. The former Carmel Congregational Church, which closed in 1999. © Gerard Charmley (2011).
Boverton, U.R.C., formerly Bethesda'r Fro (Independent). Another view. Both © Gerard Charmley (2011).

Cadoxton, Barry - see Barry and Barry Island
Cogan, St. Paul (CiW). Hebron Hall (1904). Link. Both © Gerard Charmley.
Colwinston, St. Michael and All Angels (CiW). Two interior views - 1, 2. The former Seion Calvinistic Methodist Chapel (founded 1830) and the former Ebenezer Baptist Chapel (1852) and both now private residences. All © Gerard Charmley (2011). 
Corntown, the former Bethlehem Baptist Church, now a private residence. © Gerard Charmley (2010).
Cowbridge, Holy Cross (CiW). Two interior views - 1, 2. St. Cadoc (R.C.). United Free Church. The inscription over the central window reads "RAMOTH 1828". Interior view. © Gerard Charmley. The former Ebenezer Chapel (though you'd never guess it, as a shop front has been added at a later date). © Gerard Charmley. The rear of the building reveals a more pleasing view. Gerard advises that it was Wesleyan. © Gerard Charmley (2011). The former Sion Calvinistic Methodist Chapel (aka Old Limes Chapel), now flats. © Gerard Charmley (2011).
Croes-y-Parc, Baptist Church. © Gerard Charmley. Link.

Dinas Powys.

East Aberthaw, St. Peter. Bethel Baptist Church. Both © Gerard Charmley (2011).
Ewenny, the Priory Church. © Margaret Woodley. Another view, and two interior views - 1, 2. The former Zoar Calvinistic Methodist Chapel, now a private residence. All © Gerard Charmley (2010). Link.

Flemingston, St. Michael and All Angels. © Gerard Charmley (2011).

Gileston, St. Giles. © Gerard Charmley (2011). Link.

Lavernock, St. Lawrence. ST 1864 6821. © David and Pat Halliday. Another view, © Gerard Charmley (2010). An old postcard had remained unidentified in the Unknown section for years. From Ian Lewis, Jay Priest identified it as St. Lawrence, and provided a link to an old postcard view. This Streetview is also useful, as it's from as similar a viewpoint to the Unknown as the vegetation allows. Note that the house has gone though.
Leckwith, the former St. James (CiW). © Gerard Charmley.
Llanblethian, St. John the Baptist. Interior view. Both © Gerard Charmley.
Llancarfan, St. Cadoc. © David and Pat Halliday. Another view, an interior view, and wall-paintings, all © Gerard Charmley (2011). Link. News item from the BBC. The former Bethlehem Baptist Chapel, which closed in 1981. © Gerard Charmley (2011).
Llandough, Penarth - see Penarth.
Llandough-Juxta-Cowbridge, St. Dochwdwy. Two interior views - 1, 2. All © Gerard Charmley (2011).
Llandow, Holy Trinity. © Gerard Charmley (2011). 
Llanfrynach, St. Brynach (CiW). © Gerard Charmley (2011). Link.
Llangan, St. Canna. Interior view. A stained glass window commemorates David Jones, a famous 19th century Methodist cleric. All © Gerard Charmley (2011). Link.
Llanmaes, St. Cattwg. Interior view, and some wall-paintings. All © Gerard Charmley (2011).
Llanmihangel, St. Michael. © Gerard Charmley (2011). Link.
Llansannor, St. Senwyr. Two interior views - 1, 2. All © Gerard Charmley (2011). Link.
Llantrithyd, St. Illtyd. © Gerard Charmley.
Llantwit Major.
Llysworney, St. Tydfil (CiW, O). Another view, and an interior view. SS 958 743. All © Gerard Charmley (2011). Link.

Maendy, the former Congregational Church. © Gerard Charmley (2011).
Marcross, Holy Trinity, at Nash Point. © David Gallimore. Link.
Michaelston-le-Pit, St. Michael and All Angels (CiW). © Gerard Charmley.
Monknash, St. Mary. Interior view. Both © Gerard Charmley (2010).

Penarth.
Pendoylan, St. Cadoc. © David and Pat Halliday. Bethania Presbyterian Church (1870). © Gerard Charmley (2011).
Penllyn, St. John the Evangelist. Interior view. Both © Gerard Charmley (2011).
Penmark, St. Mary. © David and Pat Halliday. Another view, and an interior view, both © Gerard Charmley (2011).
Peterston-Super-Ely, St. Peter. Interior view. Both © Gerard Charmley.
Porthkerry, St. Curig (O). From an old postcard in Reg Dosell's Collection. A modern view, and an interior view. both © Gerard Charmley (2010). One of the many churches John Wesley preached at.

Rhoose, St. Peter. Presbyterian Church, and another view. All © Gerard Charmley (2011). Jubilee Hall (1887) on Rhoose Road was built as a Gospel Mission. From 1938 until the 1960's it served as a Wesleyan Methodist Chapel, and afterwards converted to residential use. Another view. Both © Bruce Cunningham (2014). Link, showing the building before recent alterations and Bruce's photos.
Ruthin, the derelict former Calvinistic Methodist Chapel. Interior view. Both © Gerard Charmley (2011).

St. Athan, St. Athan. Another view, and an interior view. The Gathering Place (Methodist). Link. All © Gerard Charmley (2011).
St. Bride's Major, St, Bridget. Interior view. The former Horeb Baptist Chapel (1863), now a private residence. Another chapel converted to residential use is the former Bryn Zion Calvinistic Methodist Chapel. I think the datestone reads 1859. All © Gerard Charmley (2010).
St. Brides super-Ely, St. Bride (CiW). © Gerard Charmley.
St. George's super-Ely, St. George (CiW). © Gerard Charmley.
St. Hilary, St. Hilary. © Gerard Charmley.
St. Lythan, St. Lythan (CiW). © Gerard Charmley.
St. Mary Church, Church of the Annunciation of the Blessed Virgin Mary. Interior view (note the Norman drum font), and a fragment of a medieval altar. All © Gerard Charmley (2011). Link.
St. Mary Hill, St. Mary. © Gerard Charmley (2011).
St. Nicholas, St. Nicholas (CiW). Tre-Hill Presbyterian Church. Both © Gerard Charmley.

Treoes, Saron Independent Chapel. © Gerard Charmley (2011).
Twyn-Yr-Odyn, the former Baptist Chapel, now closed. © Gerard Charmley.

Welsh St. Donat, St. Donat. © Gerard Charmley.
Wenvoe, St. Andrew. St. Mary. Both © Gerard Charmley. Former Calvinistic Methodist Chapel, now a private residence. © Gerard Charmley (2010).
Wick, St. James (CiW). Interior view. Both © Gerard Charmley (2011). Unitarian Chapel. © Gerard Charmley (2010). Another view. © Gerard Charmley (2011).

Ystradowen, St. Owain. Two interior views - 1, 2. All © Gerard Charmley (2011).