As we plant our applications in the cloud we need to reorient our thinking from synchronous toward asynchronous programming. The reactive framework coming out Microsoft Live Labs is designed to help you make the transition.
With it you can move from an imperative, pull-style of programming to an event-based async model. RX works in Silverlight and with the recent announcement of JS extensions for RX you can use it in your AJAX style applications even with JQuery!