Have you ever wanted a web server written entirely in PHP? Now you can with nanoweb. A project like this really shows the power of the PHP language.
Some of the features of the application include: HTTP/1.1 implementation, Modular architecture, Authentication support, MIME support, and, of course, PHP support. There's even been some performance stats created for it to show its robustness, and installation is as easy as running an install script (or batch file).