Nginx 0mq transport layer for communicating with upstream servers 15 years ago
I've been using mongrel2 pretty much since the beginning. I host my own websites with it. Although they are very low traffic I ran some performance tests using blitz.io and the results were impressive. Less than 1% conn errors with a 512MB linode and a simple Django app (no database).
I'm also blogging about mongrel2 lately: http://daltonmatos.wordpress.com