Xaml and Media server controls
Fritz Onion has a post on his blog about these two controls. Unfortunately, my experiences with these controls didn't run very well and I don't agree with him when he says that they provide a cool model to integrate silverlight content on the page.
My main beef with them is that, unless they've changed something and have release a new version of the future bits, then those controls inject an object tag on the page instead of using js to create the new object on the fly (like the demo pages that come with silverlight do). The problem with this approach is that you get a "disabled" control which gives you a message saying that you must click to activate the control.
iAgain, it's one of those scenarios where i really can't understand why they're doing this when they've already have so cool js wrappers that could be easily embedded on the dll that has the control...