If, like me, you're a freedom-loving hippie and you like your software open source, then I'm sure you've wondered about where to get open source apps for your phone. The Google Play Store is great, but it doesn't explicitly tell you if an app is open source.
F-Droid is like the Ubuntu Software Center for your Android phone. It contains a repository of only free and open source software for Android. F-Droid has become my first port of call when it comes to applications. When I'm looking for something I'll browse through F-Droid before launching the Play store. Admittedly not all the applications are awesome, but it's a good place to start.
In addition to being a good place to find open source apps for your Android device, apps in F-Droid tend to be updated faster than their counterparts in the Play store. I am under the impression that F-Droid compiles the apps itself rather than relying on the authors or the Play store.