Check out the latest issue of windows.developer.
I contributed an article on .NET Rx (Reactive Extensions) in this issue giving an overview and an introduction to this topic.

Rx is a library to compose asynchronous and event-based programs using observable collections and LINQ-style query operators.
If you are serious about .NET development and have not worked with Rx yet make sure to get familiar with this technology. Rx will fundamentally change to way you deal with asynchronous programming, events and delegates.