SignalR - Incredibly simple real-time web for .NET

ASP.NET SignalR is a library for ASP.NET developers that makes it incredibly simple to add real-time web functionality to your applications. It's the ability to have your server-side code push content to the connected clients as it happens, in real-time. SignalR also provides a very simple, high-level API for doing server to client RPC (call JavaScript functions in your clients' browsers from server-side .NET code) in your ASP.NET application.