Has there ever been a time when you were using Linux, BSD, or just wanted an open-source version of the program you were using, but could not find one? I know I have.
Recommended to me was the site osalt.com. It is a directory of both open source programs and proprietary programs - with alternatives for the closed.
Naturally, I searched for Photoshop - and the results brought up The Gimp, Paint.NET, among other open-source programs.
A search for Visual Studio brings up some free development environments.
iTunes? Banshee, Amarok, Songbird.
Overall the site is very well organized and easy to navigate, with quick links for every program. If you ever are wondering if there is an open source program as an alternative to the ones you use, I recommend you check this site out.