When it comes to webservers on a linux based system you would 99% of the time think of Apache. Without a doubt Apache is the most popular free webserver and has plenty of resources on the web where you can seek help (http://httpd.apache.org) there are however a number of other free as well as commercial webservers available for other applications.

Apache – http://httpd.apache.org
Most well-known webserver software, with versions available for unix and windows. Currently has two stable releases 1.3.x and 2.0.x

Boa – http://boa.org
Can handle a huge amount of requests per second compared to other webservers. Configuration is very similar to that of apache

Caudium – http://caudium.net
Caudium has both stable and development releases, it has Pike and RXML support.

Roxen – http://roxen.com/products/webserver
Highly graphical webserver. Built around the Pike object orientated language.

Thhtpd – http://acme.com/software/thttpd
Flexible and occupies a small memory footprint. Basic server without high end capabilities.

Tux / kHTTPd – http://kernel.org
Webserver as a loadable kernel module. Unique.

Zues – http://zues.com
Considered the best enterprise level server. Users include ebay and red nose day. Huge amount of features. Price tag of £1100


1. Apache – Pre-fork; CGI; PHP; VHosts; Auth; No Throttling
2. Boa – Select; CGI; VHosts; Auth; Chroot; No Throttling
3. Caudium – Threads; CGI; PHP; VHosts; Auth; Chroot; No Throttling
4. Roxen – Threads; CGI; PHP; VHosts; Auth; Chroot; No Throttling
5. Thttpd – Select; CGI; Auth; Chroot; Throttling
6. Tux – Select;
7. Zues – CGI; PHP; ASP; VHosts; Auth; Throttling

Pre-fork: Start a pool of processes which each handle multiple requests
Threads: Use threads instead of processes/
Select: Use non-blocking I/O and the select() System call to handle multiple requests in a single process, single thread.

Adding to the list:
AOLserver http://www.aolserver.com/
AOLserver is a multithreaded, Tcl-enabled, massively-scalable and extensible web server tuned for large scale, dynamic web sites. AOLserver also includes complete database integration and a dynamic page scripting language.

Ironic as it seems that AOL does not provide a client for linux but many of their servers run on a *nix based system.

This is very useful information guys. The one unfortunate thing is that threads like this often disappear down the forums and the information isn't as easily accessible for reference. This is one reason that the LQ Wiki was set up.
http://wiki.linuxquestions.org/wiki/Main_Page

If you find time to add some of your information it would be most appreciated by the whole community I'm sure:
http://wiki.linuxquestions.org/wiki/List_of_web_servers