Religious records

Ancestors Reunited
A commercial company offering a gravestone/church photography service based in Scotland and covering the entire UK.
Family Search
Family Search, the LDS genealogy site. Contains a lot of information from church registers prior to civil registration.
FreeREG
The FreeREG Project’s objective is to provide free Internet searches of baptism, marriage, and burial records, which have been transcribed from parish and non-conformist church registers in the UK
Genuki
Covers every county in the UK and includes information on places, libraries, archives, family history societies. Many Trade Directories and Gazetteers on-line as well as census information and much, much, more.
The Jewish Genealogical Society of Great Britain
A useful site with a lot of information and links to help you with your research.
ScotlandsPeople
A website run by Scotland Online on behalf of the General Register Office for Scotland. A pay-per-view website including indexed digital images of the statutory registers of births (1855-1903), marriages (1855-1928) and deaths (1855-1953) for Scotland, the 1891 and 1901 Scottish censuses, and indexes to the 1881 census and the Old Parish Registers of baptisms and marriages.