SSE - Simple Sharing Extensions - A Microsoft innovation on RSS:

Ray Ozzie and the team at Microsoft is working on an exciting new innovation  to RSS called SSE, Simple Sharing Extensions.  There is a draft specification in place, and sample code will be ready soon. Microsoft has released the Simple Sharing Extensions specification under the Creative Commons license, the same license that covers the RSS 2.0 specification.

(Via Don Dodge on The Next Big Thing.)