International Standard Bible Encyclopedia is a free online Bible Encylopedia. It has very detailed articles on most prominent words in the Bible. Helps you to study words like Ashtoreth or Pharisee that you may not know the meaning from simply reading the Bible.
Blue Letter Bible Is a resource for looking up Strong's Dictionary and Vine's Dictionary terms. Useful for understanding Bible words in the original language.
E-Sword is a website with a Bible study program available for a free download. It has several reliable Bible translations as well as a Strong's Dictionary and several very good commentaries that are all available for free. Other Bible
Christianity.com is a great site with many resources such as videos, articles and a Bible study tool where you can study commentaries and various translations of the Bible.
Grace to You is John MacArthur's website. The great thing about this is that he has opened up the archives of the past 40 years of his preaching and made all the audio free for download. Type the topic you want to search for in the Search box at the top of the page and choose from thousands of relevant topics for your life today. This is an indispensable resource for growing Christians!
Desiring God is John Piper's website. In addition to great Bible teaching, you can also download for free in pdf format all of the books that he has written! There is a search function also. So if you want information on a topic or word, you type it in the Search box and you will see a listing of all the relevant material.
Ligonier Ministries is the home of R.C. Sproul. For years he has been one of the most renowned theologians in Christendom and in the last 12 years he has pastored a church in Florida. He has free teaching videos and articles by himself and other Christian laypersons.