Celso Gomes, excellent designer working for the WPF team (Blend, Design and Silverlight) put together a Silverlight only website with great short tutorials. I just took the “Animations” ones, and I like the concept. Short lessons, easy to remember.
Side note: This is the first Silverlight-only website I saw (after a looooong raw of Flash-only websites). While I find Silverlight much more appealing than Flash for the developers, the huge strength of SIlverlight over Flash is the ability to interact with the HTML page hosting it. So please please please, don’t make too many Silverlight-only sites, use Silverlight wisely and degrade gracefully for non-Silverlight enabled devices!