The Abyss Web Server from Aprelium Technologies is one of the neatest, tiniest web server I've come across. It's only 144 KB for the Windows version and the Mac, Linux and FreeBSD versions are around that size as well. It's also free. What's more, adding PHP support is quick and painless. Just follow the instructions for adding PHP support. I did all of it under 5 minutes (like Phil - see the source for this entry).
Why is this cool? Because it is very useful as an easy-to-setup test platform for server-side scripts like PHP, ASP and Perl scripts. Being flyweight helps too, since there are no long download times for those still using dialup modems. Everything is run via CGI - there are no modules, unlike for Apache. There is a single config file, abyss.conf, which contains Apache configuration-like directives. The good thing is, there's no need to go into the file to make changes - the web-based configuration interface provided by Abyss allows a simple click-and-point interface which is a breeze to use.
What a boon to beginners (AKA newbies) who often have trouble setting up Apache with PHP support. I'm going to recommend this as an alternative to Apache for anyone with difficulties setting that up in the future.
Source: Phil Wilson