Several posts ago I’ve mentioned interesting library developed by Microsoft - Reactive Extensions (Rx) - http://msdn.microsoft.com/en-us/data/gg577609

Few months have passed and it’s getting more and more popular: as a proof I can bring a very interesting framework for creating structured user interfaces - Reactive UI (http://www.reactiveui.net).
It uses all the power of Rx to make it able to create elegant and testable UIs according to MVVM paradigm. What’s even better, it can target not only Silverlight or WPF, but WP7 and WinRT (!) as well. Fortunately it’s free (MS-PL license) and available on NuGet (nothing can be easier than getting it then). Honestly, I haven’t give it a try yet, but it looks promising. To learn more, check the following resources:
Another motivation to finally put my hands on WinRT :)