Christianity

• Catholic
• Protestant, Orthodox & Other

Islam

• Introduction to Islam
• Islam, the Modern World, and the West: Contemporary Topics
• Centre for Islamic and Middle Eastern Law
• Institute of Islamic Political Thought
• Islam and Human Rights
• Liberal Islam Network
• Understanding Islam
• IslamOnline.net
• IslamiCity.com
• Aljazeera.net
• Islam101

Judaism

• Academic Jewish Studies Internet Directory
• Internet Resources for the Study of Judaism and Christianity
• Non-Christian Religions Generally

Social Sciences & Religion

• Religious Movements Homepage Project@UVa
• Sociology of Religion (Wikipedia)
• Fundamentalism (Wikipedia)
• Adherents.com (statistics and religious geography)