The Bible Gateway, http://Bible.gospelcom.net is a service of the Gospel Communications Network, a multimember alliance of on-line evangelical Christian organizations.  Here you can search the Bible in over a dozen English translations (and translations in eighteen other languages, too) by passage or word.  There is also a topical search page.

www.crosswalk.com is a professionally done, evangelically-oriented site with one of the best Bible study search engines on the Web.  Tools include over twenty versions of the Bible, an Interlinear and a Parallel Bible.

The Bible Researcher Site, by Michael Marlowe.  Especially useful for its parallel Bible resource: www.Bible-researcher.com 

The Five Gospel Parallels, by John W. Marshall.  Perfect for comparing gospel texts with one another: http://www.utoronto.ca/religion/synopsis/ 

Christian Classics Ethereal Library: a major site with many classic commentaries and resources.  www.ccel.org