The 2009 GitHub contest is now officially over! We would like to thank everyone that entered the contest - it was a lot of fun, produced a huge number of really amazing open source recommendation engine projects in several languages and helped get developers who are interested in this space to meet each other and compete in a fun environment.
Here are some of the projects that entered the contest and have open source code available on GitHub. If you participated in the contest and want your project listed here, please add your source code to your project and then email me (scott at github). It would be great if you describe your approach in your README, too.