Open Source
Microsoft continues its commitment to open source. We not only host projects at the CodePlex forge and support many open source projects, but we also create our own open-source projects that the community can improve and extend. There are thousands of great open source projects, applications, and libraries that you can use with ASP.NET today. Here you'll find a few of our favorites. If you're looking for Samples, there's lots of samples here as well as on http://code.msdn.microsoft.com. We'll update these pages as we come upon other cool projects. - Jon Galloway and Scott Hanselman
ASP.NET SignalR
The source code for ASP.NET SignalR is available under an open source license. Developers outside of Microsoft may submit patches and code contributions that the Microsoft development team will review for potential inclusion. The framework continues to be fully support and staffed by Microsoft.
ASP.NET SignalR Signed Nightly Builds
If you just want to try the latest feature or bug fix you can use a nightly build. While a nightly build might work, we strongly urge you to only use official builds for production. Nightly builds are meant for developers to try out new features or bug fixes ahead of an official prerelease or final build. There is no guarantee that a nightly build will be available or will work. A nightly build is just a build of what is currently checked into the source repository.
Public Continuous Integration (CI) server
The SignalR team maintains a publically visible CI server that builds the public source code repository on every check-in.
JabbR
JabbR is an open source, real-time web chat system built using ASP.NET and SignalR. Source code is at https://github.com/davidfowl/jabbr.
ShootR
ShootR is an open source, real-time, multi-player HTML5 space shooter game, using SignalR for real-time server-client communications. Source code is at https://github.com/NTaylorMullen/ShootR.
ElmahR = ELMAH & SignalR
A real-time monitoring solution for ASP.NET applications built with ELMAH and SignalR.