Online study aids
Crosswalk.com Bible study tools pageA very extensive collection of online Bible study tools, including over 20 different translations, parallel study Bible, commentaries, concordances, dictionaries, you name it.
The Blue Letter BibleA very interesting online study Bible based on the King James version, with blue letter "buttons" for every verse. Click on a button to instantly bring up cross references, concordance (with parallel Greek/Hebrew text for every word), commentaries, alternate translations, dictionary entries, even hymns and images related to the verse.
Bible.comA good place to just read the Bible. This site has 24 English translations online, including versions not available for free elsewhere (like the NIV). Check it out.
Free software
A group that develops free, cross-platform Bible study tools. Many Bible translations, commentaries, dictionaries, and study tools available for free. Makes reading 6 translations at once and cross-referencing to the Greek and Hebrew texts almost easy.
Commercial Software
Logos Bible SoftwareHome of Logos Bible Software Series X, a very good, complete, expandable Bible study system. (Hey, if it's got "X" in the name, it's got to be good, right?) From the Home library at $150 to the $599.95 Scholar's library, there's something for everybody. If you're tired of the online stuff, and are ready to spend the money on good computer based study tools, it's worth a look. Even the base Home Library is more than most people will use.