This has been around a bunch, but I figured I would give it due dilligence and post a link to the MSDN article that describes the infrastucture and provides examples:

http://msdn.microsoft.com/xml/rss/sse/

It's VERY cool technology that I've had the opportunity to mess around with, and it's potential to be a very slick and simple transport method between applications (especially PIM types) moving forward is awesome.

Anyone implemented it anywhere in an interesting way?