Wonko-web-server is a project mainly written in Ruby, it's free.
experimental preforking rack handler. and by experimental I mean: no tests.
"Wonko is what my mother called me when I was a kid and clumsy and knocked things over, and a web server is what I am!"
Preforking + EventMachine + thread pool experiment.
Supports keep-alive and async.callback.
Is fast (as in, standard setup is faster than Thin).
Do not use in production.
Wrote this in a weak moment, late at night.