Scott Hanselman who blogs at http://www.hanselman.com/blog/ has an annual blog post since 2005 in which he gathers suggestions, feedback, experience from his readers, and shares a compilation list of tools and utilities all developers should be aware of.
This list is massive with great commentary on their function and subject area of these tools (with many of them being free) - I can honestly say that I have yet to see his annual list and not find a few tools that helped make me more productive.
The list (which is like drinking from a fire hydrant) is located here http://www.hanselman.com/blog/ScottHanselmans2007UltimateDeveloperAndPowerUsersToolListForWindows.aspx
I always enjoy hearing from others on tools and utilities they have found to be valuable.
Check out this list and see if you spot anything you could be using.
"If the only tool you have is a hammer, you will see every problem as a nail" - Abraham Maslow. (This quote always sticks with me - Brad)