Unger's Bible Dictionary, by Merrill F. Unger
A volume combining geographical information, historical backgrounds, archaeological illumination and confirmation, thousands of Biblical facts, and an impartial treatment of problems of interpretation.

Evangelical Dictionary of Theology, by Walter A. Elwell
This leading reference work continues to provide comprehensive, useful and accurate information in systematic, historical and philosophical theology as well as theological ethics.

The NIV Exhaustive Concordance, by Goodrick & Kohlenberger

Strong's Exhaustive Concordance, by James Strong
(for the King James Bible translation)

New Testament Survey, by Merrill C. Tenney
A comprehensive survey of the New Testament world and the New Testament message.

A Survey of Old Testament Introduction, by Gleason L. Archer
Archer presents a systematic study of the ancient background against which the first thirty-nine books of the Bible are to be properly understood.

Generally good commentaries are noted below. Be aware that if a commentary series is for the whole New or Old Testament or for both, that usually an author is better in some books than others. There are also "critical" commentaries that do work out of the original languages and get you further into the meaning of individual works and "devotional" commentaries that are good but light reading on passages.

William Hendriksen - His commentaries would be identified as "critical" and would be mostly New Testament on individual books.

Warren W. Wiersbe - Good balance between "critical" and "devotional" commentaries. Excellent at helping you get to the point of the passage. Old and New Testament books are available.

H. C. Leupold - Commentaries by Leupold are good for those interested in the Old Testament and give solid help in understanding these books.

A. W. Pink - Pink has both commentaries and biographical studies in the Old Testament.

C. F. Keil & F. Delitzsch - Old Testament "critical" commentaries that give you lots of material and a deep sense for a passage.