For me, Silverlight has never been about rich media, so much as rich applications. So the announcement and release of Silverlight 2 was a turning point. Prior to that, Silverlight had effectively no controls – meaning no useful controls for building line of business applications.
I love these kinds of mini-sites – they demonstrate the controls so much better than a textual description can, and handily give you a test harness as well. We use a “sample” ourselves when developing custom controls.
Italian introduction : http://blogs.msdn.com/pietrobr/archive/2008/12/22/silverlight-2-controls-demo.aspx
Silverlight 2.0 Controls Sample : http://silverlight.net/samples/sl2/silverlightcontrols/run/default.html
Silverlight Control Toolkit Sample : http://silverlight.net/samples/sl2/toolkitcontrolsamples/run/default.html