Check out Soma's blog today:

He announced a new project called Silverlight that enables amazingly cool cross browsers, cross platform web apps to be written.  I've seen some of the demos and they are stunning.  I suspect over the next week or two we'll see lots of demos posted to give you an idea of what you can do.  You can check out for more information and a video of the kinds of things you can do (OK, I can't do them because I have the artistic ability of your average 3 year old, but it's amazing to see what others can do with it :))