Sites with information about historic churches elsewhere
these sites are all recommended and many of them have links to other sites of interest

in general
Anglo-Saxon Churches
Baptisteria Sacra: fonts of the world
Churchcrawler
Church Monuments Society
Corpus Vitrearum: medieval glass
Ecclesiological Society
Monumental Brass Society
St Nicholas Center
West Gallery Churches

meet the neighbours
Cambridgeshire
Essex
Peterborough

further afield
Bedfordshire
Buckinghamshire
Cheshire
Kent
Leicestershire and Rutland

Please feel free to recommend a site.