Silverlight is here

Microsoft has released a plug-in for delivering next generation media experiences and rich interactive applications for web. This is a cross-browser, cross-platform plug-in which facilities the WPFs' rich look and feel.
Silverlight was formerly known as WPF/E.
Besides me telling you about Silverlight go to Microsoft and see for your self, you also can find some nice samples done.

http://www.microsoft.com/silverlight