e-Sword Bible Software (mostly free)

You can never spend a dime and find this application useful or you can spend a few dollars and make it absolutely great.

Logos Bible Software (mostly paid)

Costs to get started, afterwards, there are some free resources available.

Bible.com

Online Bible and other resources

Bible History Online

Maps, Study Tools, History and more!

Christians Unite

Another online Bible Resource

RBC Ministries

Publishers of "Our Daily Bread"