Religion from KnowUK [24/7]
Religion or philosophy from Oxford Reference Online [24/7] [Can't get in?]
Religion from CredoReference [24/7]
Calendars and time - Links to lots of calendar resources, including Islamic and Jewish calendars.
Adherents.com - Collection of figures with references to published membership/adherent statistics and congregation statistics for many religions, denominations, faith groups, tribes, etc.

Oxford Islamic Studies Online [24/7] - Containing nearly 3500 reference articles, bringing together current scholarship in the field and promoting understanding of the Islamic world.
Sacred Texts Archive - Links to the sacred texts of a wide range of belief systems.
Virtual Religion Index - Links to information and resources on a vast range of religious topics, intended to further research.
BBC Religion - Features include guides to a variety of religions, discussion forums, calendars, what's in the news, ethical issues and more.

Stanford Encyclopedia of Philosophy - Constantly updated and comprehensive encyclopedia of ideas
Philosophy around the web - Gateway to philosophical information - scroll down the home page to get to the content.

Encyclopedia Mythica - Clear site on myths and folklore around the world. Over 7000 articles with good cross-references and pictures.
Bulfinch's Mythology - Online version of the classic Nineteenth Century work on mythologies - "the age of fable or stories of gods and heroes".

Occultopedia - An encyclopaedia of "the occult and the unexplained", with good cross-referencing and details of books and other sources of information. Can be searched alphabetically or by topic.