I'd missed this announcement over at Windows Live - it's quite a long one but the interesting bits for me were;

1. New Windows Live Messenger API. This is a Javascript library rather than (say) a .NET library but it allows you to build Messenger capabilities straight into your own pages. I've tried the demos but I've not read the API docs yet - I'd be curious to see how difficult it is to call that API from .NET code.
2. Silverlight Streaming ups its limit to 10GB and also offers both a WebDAV API along with transcoding capabilities - cool. Silvleright Streaming is about my favourite service from the Live guys.
3. It sounds like data-based services will line up around AtomPub just like ADO.NET Data Services does so that might be pretty cool in terms of re-using the client side bits of ADO.NET Data Services.
4. And some more announcements around delegated authentication, tooling and so on.

Check it out - I've just gone off to browse the Messenger API and it is looking like it's heavily wedded into script :-( It'd be great to see a service that I can just add a reference to from Visual Studio :-)