One of the coolest new features in Silverlight 3 (and now 4) is the ability to add multi-touch capabilities to your web application.
This capability opens-up all kinds of new possibilities – especially with the popular new multi-touch hardware systems available these days like the TouchSmart PC.
Multi-touch support is becoming standard in the various Windows APIs and frameworks. Support is built into Windows 7 and the forthcoming Windows Presentation Foundation (WPF) 4. Microsoft Surface computer is also based on WPF as well, but includes custom extensions for its unique capabilities.
Check-out this MSDN Article by Charles Petzold that focuses on the multi-touch support in Silverlight 3.
Exploring Multi-Touch Support in Silverlight: http://msdn.microsoft.com/en-us/magazine/ee336026.aspx
See what Multi-touch support could do for your next web applications!