From the one-less-thing-for-me-to-do department, Chris Dix has created a managed wrapped of the WinXP P2P SDK. He also has several sample apps, including a Scoble-inspired MagicFolder. According to his site, Chris plans to extend his library to support web services (WSE custom channels?) which should be very cool.
It's funny, I used to get really sad when I discovered someone else had built something that I had started building. Especially if, as in this case, theirs was better. Now, I'm just relieved that I can reuse the library without having to build all the surrounding infrastructure. I'm glad I never released my managed P2P wrapper, it would be one more thing for me to kill. Like my HtmlReader stuff. I still get people looking for it even though I killed it a while ago. (Hasn't everyone figured out they should use SGML Reader instead?)