Concordances are used to find the locations of specific words in the Bible. There are different concordances for different translations and many of them are keyed to the Hebrew or Greek text.
ESV comprehensive concordance of the Bible by 
The NIV Complete Concordance by 
The NRSV Concordance by 
Strongest Strong's Exhaustive Concordance of the Bible by 
The Hebrew English concordance to the Old Testament : with the New International Version by 
The Exhaustive Concordance to the Greek New Testament by When choosing a commentary, there are a few things that you will want to keep in mind. The first thing is what is the intended audience for the commentary. Some commentaries are more technical in nature and are designed primarily for academics who are interested in textual, theological, and historical questions. Other commentaries, often termed exegetical commentaries, are designed to help pastors and Bible teachers in their preparation of sermons and Bible studies. Yet another audience for commentaries is layperson who is looking for material for his or her own personal study. The other thing that you will want to keep in mind is the theological perspective of the author. Some authors will approach the Bible as a text like any other ancient text while others will approach the Bible as the word of God (a low versus a high view of Scripture). In addition to the author's view of Scripture, the author's theological tradition is also important. That is, it is important to understand if the author comes from a Catholic, Orthodox, Lutheran, Calvinist, Anglican, Anabaptist, or Wesleyan-Arminian background. There are two ways of doing this. First, you can find out information about the author; if that information is limited, you can learn about the publisher--different publishers target different audiences and theological perspectives.
Lexicons are similar to dictionaries in that they provide definitions of the Hebrew and Greek words that are used in the Bible. Unlike most dictionaries, they often focus on the historical context of the words, that is, how those words were used in other Hebrew and Greek texts that were around at the time of the Bible's composition.
A Greek-English Lexicon of the New Testament and Other Early Christian Literature by 
The new Brown - Driver - Briggs - Gesenius Hebrew and English lexicon by Unlike most dictionaries, Bible dictionaries tend to be more like encyclopedias. They are a resource that you will want to use to get a quick overview of an important topic, word, or person that is related to the Bible.
The Anchor Bible Dictionary by 
Holman Treasury of Key Bible Words by 
