In case you can’t get enough of Microsoft videos, there’s now a dedicated site for them in testing: http://preview.microsoft.com/video/. Built using Silverlight, the new Microsoft Video website looks to be a great central point for finding and viewing official Microsoft videos, and includes content from other Microsoft sites such as Channels 8, 9 & 10.
Performance is great, though quality is sometimes patchy when in full-screen mode. I especially love the on-screen controls, and in particular the mouse-over transition effects. Very cool. Full marks goes for including RSS feeds for searches, for example this feed for Windows Live.
While content is US only at the moment, the About page explains that they hope to add more content from other Microsoft offices around the world. Lets just hope they stick to the informative videos and less of the viral marketing!