Mongrel

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.
WEBrickと比較してそんなに早く感じないけど...
WEBrickとMongrel、SGMLとXML