Mongrel2: The Language Agnostic Web Server

Mongrel2 is an application, language, and network architecture agnostic web server that focuses on web applications using modern browser technologies.

Features

Language Agnostic with a simple backend protocol supporting 17 languages and platforms all written by Mongrel2 fans.
Modern Browser Friendly designed to handle HTTP, Flash XMLSockets, or WebSockets, Long Polling on the same socket transparently.
ZeroMQ Enabled as well as HTTP proxy support so it works with what you have already while giving you new super powers.
Network Architecture Agnostic so you can carve your operations up any way that reduces costs.
N:M Messaging Patterns means you can have any N handlers answer to any M browsers arbitrarily, but still easy to do plain request/response.
Automation Loving Configs that are easily accessible via any programming language with a Model-View-Controller design.
Modern Internal Design using the Mongrel 1 HTTP parser powering many big companies with a proven security track record, event based I/O, fast coroutines to handle that I/O, and smart reasonable defaults with zero configuration needed usually.
Documented, Documented, Documented. We document everything in a well written manual that shows you how to use every feature.
BSD Licensed and all with a BSD 3-clause license.
Tir -- An official framework written in Lua that shows how to use Mongrel2 to create other frameworks for PHP, Python, etc.