The BBC World Service Guide to the Religions of the World has clear explanations of the basics of Islam, Hinduism, Christianity, Buddhism, Judaism and Sikhism.
Religions of the World is part of the eMuseum at Minnesota State University, Mankato. Covers Islam, Hinduism, Christianity, Buddhism, Judaism and Animism. Amateurish layout and design make it difficult to read, which is a pity; there's lots of good info there.
Adherents.com concentrates on religion statistics and geography. The site is non-sectarian and in fact doesn't include information about doctrines. It does have http://www.adherents.com/adh_links.html
Ecumenical Links - Religions of the World offers an alphabetical listing of different religions of the world and various web sites associated with them.
General Links, African Traditional Religions, Bahá'i, Buddhism, Hinduism, Islam, Judaism, Taoism and apparently plans for more. Ecumenical links is maintained by the World Council of Churches as a service to the ecumenical community.
Academic Info's Religion Gateway is ad-riddled, but has a huge collection of links.
The World of Religions / Sacred Texts of Various Faiths includes links to