Looking for an open source application to one of your proprietary ones? Not sure what’s out there in a particular category? Then you definitely need to visit the OSALT website. Osalt, or Open Source As Alternative, lists top open source applications and top proprietary applications. Right from the front page you can begin finding good OSS alternatives to programs such as Photoshop, Citrix, iTunes, and Nero Burning ROM. For instance, it lists Amarok (I use this one!) and Songbird as alternatives to iTunes. I definitely recommend Amarok, as I use it. Songbird is a great choice, although they recently stopped Linux development.
On the site, you can click one of the Top 10s and see a review of the application. Looking at Dia, for instance, you will see a link to the website, a brief description, a rating (3 out of 5 stars), and other apps similar to Dia. Dia, if unaware, allows you to receive some of the Visio functionality. In schools, we use it in place of Inspriation.
You can also just search or go through the directory. A definite must is to subscribe to their RSS feed, to receive updates of new software. Osalt definitely will help you in finding the Open Source alternatives to go an open source world!