I'll be giving a talk on Manos de Mono (http://jacksonh.tumblr.com/post/1159500924/manos-de-mono-the-manifesto). It is inspired by Friend Feend's Tornado web server, but written mostly in C# using a non-MS stack. It is backed by libev which is the same as Node.js. It actually runs best on Linux- like platforms. It was started by Jackson Harper on the Mono team.
The framework it is still in the early stages, but it is looking promising. A recent benchmark showed it was able to process 10k+ requests per/sec. It is targeted as a thin "web framework" and is also embeddable.