nginx

nginx [engine x] is a HTTP server and mail proxy server written by me (Igor Sysoev).

nginx has been running for more than four years on many heavily loaded Russian sites including Rambler (RamblerMedia.com).
In March 2007 about 20% of all Russian virtual hosts were served or proxied by nginx.
According to Google Online Security Blog year ago nginx served or proxied about 4% of all Internet virtual hosts.
2 of Alexa US Top100 sites use nginx.
According to Netcraft in December 2008 nginx served or proxied 3.5 millions virtual hosts. And now it is on 3rd place (not counting in-house Google server) and ahead of lighttpd.
According to Netcraft in March 2009 nginx served or proxied 3.06% busiest sites.
According to Netcraft in May 2009 nginx served or proxied 3.25% busiest sites.
Here are some of success stories: FastMail.FM, Wordpress.com.

The development stable versions are nginx-0.8.4, nginx/Windows-0.8.4, the change log.
The latest stable versions are nginx-0.7.61, nginx/Windows-0.7.61, the change log.
The latest legacy stable version is nginx-0.6.38, the change log.
The sources are licensed under 2-clause BSD-like license.

English Resources:

The Russian documentation.

Basic HTTP features:

Mail proxy server features:

Tested OS and platforms:

Architecture and scalability:

Other HTTP features:

Experimental features: