XAMPP is a very easy to install Apache Distribution for Linux, Solaris, Windows and Mac OS X. The package includes the Apache web server, MySQL, PHP, Perl, a FTP server and phpMyAdmin.
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 httpd has been the most popular web server on the Internet since April 1996, and celebrated its 15th birthday as a project this February.
Nginx is a free, open-source, high-performance HTTP server and reverse proxy, as well as an IMAP/POP3 proxy server. Igor Sysoev started development of Nginx in 2002, with the first public release in 2004. Nginx now hosts nearly 11.28% (43M) of all domains worldwide. Netcraft predicts that current trends will soon have Nginx surpassing Microsoft IIS as the second most popular web server.
Nginx is known for its high performance, stability, rich feature set, simple configuration, and low resource consumption.
Nginx is one of a handful of servers written to address the C10K problem. Unlike traditional servers, Nginx doesn't rely on threads to handle requests. Instead it uses a much more scalable event-driven (asynchronous) architecture. This architecture uses small, but more importantly, predictable amounts of memory under load.
Even if you don't expect to handle thousands of simultaneous requests, you can still benefit from Nginx's high-performance and small memory footprint. Nginx scales in all directions: from the smallest VPS all the way up to clusters of servers.
Security, speed, compliance, and flexibility -- all of these describe lighttpd (pron. lighty) which is rapidly redefining efficiency of a 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, SCGI, Auth, Output-Compression, URL-Rewriting and many more) lighttpd is the perfect solution for every server that is suffering load problems. And best of all it's Open Source licensed under the revised BSD license.