Bible Study Resources

http://www.biblegateway.com

Bible in several versions/translations and languages, search by verse, by word (concordance) and by topic. No commentaries

Blueletter Bible

Bible in major versions/translations, search by verse and by word (concordance). Analysis of correlating passages, Hebrew/Greek words, variety of commentaries (JV McGee, Chuck Smith, David Guzik, Matthew Henry, Jon Courson, Chuck Missler etc), Biblical dictionary

David Guzik Bible Commentary 
Concise, complete and structured commentaries by book, chapter and verse of the whole Bible. Balanced and easy to read and understand (Recomended)

Also, chapter by chapter sermons on free downloadable mp3 (This guy teaches at the CC Bible College in Germany; he is not boring at all) Also, topical lectures on church history and other relevant Biblical and practical matters as well as common Q&A

Thompson Chain Reference Bible Online containing 3738 entries cross-referenced and cross-linked of topics/verses in the Bible. (Great resource, recomended)

http://scripturetext.com/

View in one screenshot a parallel comparison of Bible verses in different versions / translations, lexicon, cross-reference etc

http://www.e-sword.net/