On the Shadow Fox Network, there's a new tutorial that shows how to combine the Apache mod_rewrite functionality with some PHP functions to make passing variables over your rewritten URL easy.

You can't pass variables well without adding more commands to mod_rewrite. So here you'll learn to add unlimited parameters to your links with only one simple PHP function.

He starts with a mini-refresher course on the contents of the previous article and moves to the simple rewrite example that makes it possible - a two line statement. Then, it's on to the PHP - again, a simple function that does things simply, grabs all of the parameters from the URL and splits them out into a global parameters array. He even includes a simple example as a tutorial you can try out with the demo.