I posted before about use of Silverlight for the Halo3 videos - I've got to say the whole museum of humanity series is an impressive piece of work just to support Halo. There's also a an interactive manual that's well worth a look.
I'm disappointed to see that both Halo3.com and the root MSN Halo site use Flash where they could use Silverlight: Actually I said in a discussion that "If I worked in the Silverlight team I'd take it is a kick in the teeth...". A couple of the Silverlight team told me off for being quite so outspoken, though I'm not alone, one said
While we appreciate the passion and support, collectively these sorts of posts seem to imply that we are either too ignorant to realize when we've been kicked in the teeth, too pusillanimous to stick up for ourselves, or we're fighting like mad behind the scenes but losing. These all assume that we have been kicked in the teeth, which is simply not true.
OK. Fair's fair: Silverlight is still new, still building its base of developers and (as I've been keen to say myself) isn't a 1:1 replacement for Flash. So there are still places where Flash is the right tool for the job (not being a web developer I'm not the person to explain what these are vs what Silverlight's strengths are). On a project the size of Halo3 I suspect the lead time meant they had to go mostly with a technology which was out months ago, Silverlight would have been seen as a risk. And the Flash on these sites is Good Flash - Not the the look-at-me look-at-me adverts or We've nothing to say but paid our designers a lot usage that I think of as Bad Flash.
Over on XBox.com they've got a tool for doing your own Halo3 themes: like this one is done in Flash. Enjoy.