http://www.blueletterbible.org/index.html This is a searchable concordance with commentary, Hebrew/Greek dictionaries, hymns and other tools attached. It’s really quite extraordinary.
http://www.biblegateway.com/ This is an online concordance. You can search for both words and passages in a variety of Bible translations.
www.biblestudytools.net/ This is your one-stop shop for personal bible study. It has everything from concordance tools, commentaries, sermon helps, to a nifty parallel tool for looking at different translations of a single verse. It does not have the NIV or its tools, however. Furthermore, its Greek and Hebrew stuff is all transliterated.
http://gospeloutreach.net/bsr.html Much of this site links to the previous one but it is very cool and has an audio Bible that works with Real Player. Put your mouse on the bookshelf to see all the options available.
www.ntgateway.com/multibib.htm This site offers a broad array of search abilities both in the biblical text as well as resource materials and journals.
www.carm.org/dresources.htm This site contains an incredible array of links from apologetics to politics, from cults to theology.
www.ccel.org This is an unbelievable array of classics online. We’re talking full text, everything from Augustine to Wesley. This will save you hundreds of dollars and a lot of shelf space.
www.iclnet.org/pub/resources/christian/history.html If you are interested in reading the church fathers, this is your site. Full text is available.
www.liberty.edu/resources/library/public/re/bible/bible.htm This site has a good variety of Bible resources online. But its unique and valuable addition is its array of foreign language materials. This would be helpful for Bible studies on foreign soil.
www.perseus.tufts.edu/ The Perseus Project is an evolving digital library of resources for the study of the ancient world, particularly Greek and Latin. It is full of texts and pictures with a search engine to boot. This is a top-flight site.