This new tutorial from NETTUTS.com (by Joseph Pecoraro) takes a more detailed look at the mod_rewrite module for Apache and shows how it can work with PHP to grab information directly from the URL.
When people think of .htaccess configuration the first thing that pops into most people's minds is URL manipulation with mod_rewrite. People typically get frustrated with mod_rewrite's complexity. This tutorial will walk you through everything you need to know for the most mod_rewrite tasks.
He looks briefly at what the module is, what it can let you do and how to get it up and running on your web server instance. For his purposes, he puts his rewrite rules into an .htaccess file in the project's directory for easy updating (as opposed to part of the main Apache config files). He gives several examples of pattern matching and regular expressions to take the given URL and massage it into something else. A PHP example shows how to grab the rewritten information from the URL and put it into an example page.