Find it at http://www.ddjsilverlight.com/
As far as I know. This is one of the first portals dedicated to Silverlight by an established, major web presence other than Microsoft. However, here’s a big no-no:
Why is your header in Flash for a Silverlight Portal? Aside from this faux pas, the site seems to be pretty nice with a Silverlight-based DDJ e-zine, a tutorial showing how to develop your own Silverlight "Breakout" clone, and forums among other features. Go check it out (if you can forgive them for using Flash on the front page.