Top 50 Open Source Alternatives
Top n lists are two-a-penny in the world of computing, and collections of open source alternatives to proprietary are pretty common. This one has the virtue of offering a paragraph on each, so you have a better chance of deciding if something's worth following up.
The same site has some other lists that may be of interest: Top 25 GNU/Linux Games, and an intriguing list of "brave" hosting companies that won't (it is claimed) dump you when the going gets a smidge tough.