Nginx [engine x] is an HTTP and reverse proxy server, as well as a mail proxy server written by Igor Sysoev. It has been running for more than five years on many heavily loaded Russian sites including Rambler (RamblerMedia.com). According to Netcraft nginx served or proxied 7.50% of the busiest sites in January 2011.

PPA:
https://launchpad.net/~nginx/+archive/stable (Latest stable release)
https://launchpad.net/~nginx/+archive/development (Latest release)
https://launchpad.net/~nginx/+archive/nightly (Latest build from head)
https://launchpad.net/~nginx/+archive/community (Community build -- Read description)