LEADING OPEN SOURCE HTTP SERVERS
The Apache HTTP Server Project is an effort to develop and maintain an open-source HTTP server for modern operating systems including UNIX and Windows NT. The goal of this project is to provide a secure, efficient and extensible server that provides HTTP services in sync with the current HTTP standards.
Apache has been the most popular web server on the Internet since April of 1996. The October 2003 Netcraft Web Server Survey found that more than 64% of the web sites on the Internet are using Apache, thus making it more widely used than all other web servers combined.
Jetty is an open-source, standards-based, full-featured web server implemented entirely in Java. It is released under the Apache 2.0 licence and is therefore free for commercial use and distribution. First created in 1995, Jetty has benefitted from input from a vast user community and consistent and focused development by a stable core of lead developers. There are many more examples of Jetty in action on the Jetty Powered Page that has selections from among the tens of thousands of production Jetty instances.
Security, speed, compliance, and flexibility–all of these describe LightTPD which is rapidly redefining efficiency of a HTTP webserver; as it is designed and optimized for high performance environments. With a small memory footprint compared to other web-servers, effective management of the cpu-load, and advanced feature set (FastCGI, CGI, Auth, Output-Compression, URL-Rewriting and many more) LightTPD is the perfect solution for every server that is suffering load problems.
Nginx [engine x] is an HTTP(S) server, HTTP(S) reverse proxy and IMAP/POP3 proxy server. It’s pretty efficient for high volumes web sites, especially when serving static files.
OTHER OPEN SOURCE HTTP SERVERS
Roxen WebServer is a full-featured open-source web server distributed under the GPL license. It runs on a number of different operating systems including Windows, Linux, Solaris and Mac OS X.