Below are a number of useful links, this is in no way complete and if you have websites you think would be a good addition please contact me:
Union Lists
AULOTS – an equivalent Union list for ANZTLA (Australian and New Zealand Theological Libraries Association)
Theological Library Associations
ABTAPL Association of British Theological and Philosophical Libraries
ANZTLA Australian and New Zealand Theological Libraries Association
ATLA American Theological Library Association