It's nice when someone else does all the work for you. I ran across this post at downloadsquad.com that compiles several lists of applications from Linux users:
Sure, you know there are open source alternatives to many of your favorite programs, but who has the time to track them down?...Apparently plenty of people do, because we've found at least three good lists of Linux equivalents for Windows software.
Go check them out and let us know if there are any gems of yours that are left out. It never hurts to have a handy list like this for new converts who are missing their old Windows tools. Here's the first list from the Linux Alternative Project.