The Rx.Net Team has announced a new version of Reactive Extensions for .NET. Rx is a library for composing asynchronous and event-based programs using observable collections.
Rx is a superset of the standard LINQ sequence operators that exposes asynchronous and event-based computations as push-based, observable collections via the new .NET 4.0 interfaces IObservable<T> and IObserver<T>. These are the mathematical dual of the familiar IEnumerable<T> and IEnumerator<T> interfaces for pull-based, enumerable collections in the .NET Framework.
Rx allows programmers to glue together complex event processing and asynchronous computations using LINQ queries over observable collections such as .NET events and APM-based computations, PFx concurrent Task<T>, the Windows 7 Sensor and Location APIs, SQL StreamInsight temporal event streams, F# first-class events, and async workflows.
Learn more at DevLabs: Reactive Extensions for .NET (Rx)