Is there useful Bible software?

I currently do not use any Bible software. I have been following the development of Logos Bible Software for Mac and wonder if I might want to purchase it in the future. I also wonder if there is a quality online resource that would serve a similar purpose. I have a sense that Bible software would be a useful tool to improve my teaching, preaching and study.

Have you used or do you use Bible software? In what ways have you found it to be helpful? Do you have any suggestions on a particular software or online resource?