Some cool stuff is being done with WPF and Silverlight of late. The offical SL release is now out as well as Alpha 1.1 for developers (get them here).
Moonlight is on its way, which with help from Novell will mean Linux users will be able to experinces SL too.
A guy named Jose Fajard from Sydney, Australia (AKA LiquidBoy AKA AdvertBoy) has been doing some cool stuff with a pretty quick turn-around.
Check out this dudes site:
He has a sweet little blog explaining how he is buildiong an online version of iTunes and has a nice bunch on Silverlight controls... ready for download.
Demo of the controls on his "Beautiful Website"
Source code here on Codeplex for the iTunes app (and for the controls I believe)