Apache HTTP Server - Apache httpd has been the most popular web server on the Internet since April 1996
nginx - A high performance free open source web server powering busiest sites on the Internet.
lighttpd - A secure, fast, compliant, and very flexible web-server that has been optimized for high-performance environments
mini_httpd - mini_httpd is a small HTTP server for low or medium traffic sites.
Droopy - Droopy is a mini Web server whose sole purpose is to let others upload files to your computer.
Cherokee - High-performance web server