Don't know whether people here will be interested or not, but if you're looking to do some peer-to-peer development for applications other than file-sharing applications, you might be interested in checking out Project JXTA (www.jxta.org). JXTA is an XML-based framework providing all of the basics required when building P2P applications, and has been submitted to the IETF for standardization.

Incidentally (hint, hint), I just finished at book on JXTA for New Riders, and the entire thing is available for free off of: www.brendonwilson.com/projects/jxta