Religious organizations are sometimes the only documentation we may find for our ancestors; especially during the pre-census years. Here are some religious links that may be helpful:

The Church of Jesus Christ of Latter Day Saints
http://www.familysearch.com

Catholic Archives:
http://www.catholic-history.org.uk/catharch/index.htm

Catholic Family History Society
http://www.catholic-history.org.uk/cfhs/

Scottish Catholic Heritage:
http://www.catholic-heritage.net/

Methodist Genealogy:
http://www.kindredtrails.com/RELIGION_Methodist.html

Historical Society of the United Methodist Church
http://www.historicalsocietyunitedmethodistchurch.org/genealogy.htm

Amish
http://www.kindredtrails.com/RELIGION_Amish.html

Mennonite
http://homepages.rootsweb.com/~jrd/j__menn.htm

Baptist
http://www.kindredtrails.com/RELIGION_Baptist.html

http://homepages.rootsweb.com/~baptist/

http://www.baptisthistory.org.uk/page04.php

Jewish
http://www.kindredtrails.com/RELIGION_Judaism_Jewish.html

http://www.jewishgen.org/

http://www.genhomepage.com/jewish.html

http://jewishwebindex.com/

http://www.ancestry.com/learn/library/article.aspx?article=4119

Quakers
http://www.rootsweb.com/~quakers/

http://www.geocities.com/Heartland/Plains/2064/squaker.htm

http://www.quaker.org/