I need to know what the best lightweight, multithreaded Windows web server is for running Ruby on Rails applications. I am currenlty using thin, but it is not multithreaded (by design).
So, what are people using on Windows?
WAMP server will satisfy all of your prerequisites: http://www.wampserver.com/en/ It stands for *W*indows, *A*pache, *M*ySQL, *P*HP. It is multi-threaded and can run rails. It is very lightweight yet very customizable.
Here's also a guide for configuring Rails on WAMP: http://stmogilny.wordpress.com/2008/11/24/setting-up-ruby-on-rails-with-wamp/
How hard of a requirement is Windows? Could you run a Linux VM to run rails?
Performance wise they should at worst be comparable. I'd be willing to bet that you would see a Linux VM run rails faster than the Windows host could.