• Bible.org
• Bible Study Tools
• Crosswalk.com
• The New Testament Gateway
  
• Studylight.org
  

Christian Apologetics

• A Christian Thinktank
• Answering Islam
• Apologetics 315
• Center for Reformed Theology and Apologetics
• Christian Apologetics and Research Ministry
  
• Leadership U
• Real Messiah
• For an Answer
• Tekton Apologetics Ministry

Christian Writings

• Early Christian Writings
• Early Church Fathers
• Early Church Fathers - Additional Texts in English
• Vatican Archive
• The Paul Page
• The Tertullian Project
• The Works of James Arminius
• Selected Works of Martin Luther
• Westcott & Hort Resource Center
  The Didache translated by Rick Brannan

Jewish Writings

• Babylonian Talmud
• Chassidic Texts
• Jewish Encyclopedia
• Megillah with Commentary
• Mishneh Torah (Hebrew)
• Tanach with Rashi
• The Works of Philo

Online Books

• Christian Classics Ethereal Library
• Desiring God Resource Library
• The Gifford Lectures
• Google Books
• Internet Archive
• IVP New Testament Commentaries
• Peter Toon Books