Mongrel is a fast HTTP library and server for Ruby that is intended for
hosting Ruby web applications of any kind using plain HTTP rather than
FastCGI or SCGI.

It is framework agnostic and already supports Ruby On Rails, Og+Nitro,
and Camping frameworks.  It also supports a complete plugin system
based on RubyGems called GemPlugins.

WWW: http://mongrel.rubyforge.org/