Are you building websites that needs real-time updates? For example, Facebook and twitter feeds or stock quote updates? SignalR may be the solution for you.
SignalR is an Async library for .NET to help build real-time, multi-user interactive web applications.
From SignalR website:
ASP.NET SignalR is a new library for ASP.NET developers that makes it incredibly simple to add real-time web functionality to your applications. What is "real-time web" functionality? It's the ability to have your server-side code push content to the connected clients as it happens, in real-time.
Check out more details and download here
SignalR can be used to add any sort of "real-time" web functionality to your ASP.NET application. While chat is often used as an example, you can do a whole lot more. Any time a user refreshes a web page to see new data, or the page implements Ajax long polling to retrieve new data, is candidate for using SignalR.