Sorry not an OSS project (at least not yet). I've got one work project on GH and one "nights and weekends startup" project both in private repositories. But I like the workflow of using git for my source control versus something like TFS. Although I admit I initially picked it up just because I wanted to learn something new, I used GH instead of a local git repository because my side project has another collaborator.

EDIT: my beef with Codeplex is that I just don't find it very usable when I'm researching something. Purely as a repository for things like NuGet packages it's probably fine.