Bible

Biblegateway.com (Search)
Interlinear Bible (English - Hebrew - Greek)

Bible Dictionaries

Baker's Evangelical Dictionary
Smith's Bible Dictionary

Biblical Background and History

Sketches of Jewish Social Life (Edersheim)
The Temple: It's Ministry & Service (Edersheim)
Antiquities of the Jews (Josephus)
History of the Jewish War (Josephus)

Biblical Maps and Archeology

Visual Bible Alive
Bible Atlas

Book by Book Commentaries

Psalms (Spurgeon)
Galatians (Luther)

Christian History

History of the Christian Church (5 vols, Henry C. Sheldon)
History of the Christian Church (8 vols, Philip Schaff)

Christian Cultural Research

Barna Research Group
Family Research Council
Focus on the Family

Classic Christian Resources

Ccel.org (Christian Classics Ethereal Library)

Commentaries

Soniclight.com (Dr. Tom Constable of DTS)
Bible.org (Professors/Students of DTS)
Believer's Chapel (Dr. S.Lewis Johnson)
Scofield Reference Notes

Creation Science

The Creation Research Society
Institute of Creation Research

Cross-referencing

Treasury of Scripture Knowledge (RA Torey)

Early Church Fathers

Early Church Fathers (38 vols)
Early Church Fathers (additional texts)

Encyclopedias

The International Standard Bible Encyclopedia

Harmonies

Harmony of the Gospels
Parallel Gospels

Theology

Monergism.com (Reformed)
Theopedia (Reformed)

Weights and Measures

Weights and Measures

Word Studies

Robertson's Word Studies on the New Testament