I was roaming around the web and ran into a web application that used Silverlight this weekend. I did a little investigating and this weems to be Microsoft's answer for Flash and Rich Internet Applications in general. They make a lot of interesting claims about cross browser compatibility (IE, Firefox, and Safari) and compatibility with existing backends and AJAX. The big score for it though seems to be the claim that it is fully accessible and that the toolkit helps you make your apps more accessible and l10n. Overall, it looks pretty compelling and fairly easy to learn so I plan to keep an eye on it and see where it goes.
A really cool use of Silverlight:
A blog/analysis of it from a developer prespective:
A demo/interview of Silverlight on Youtube:
Linux related project (Moonlight):
Related (competing) projects:
Adobe AIR: http://labs.adobe.com/technologies/air/
Google Gears: http://code.google.com/apis/gears/