While it's not exactly PHP related, there are some tips in a new article from DevShed.com that can make the search engines adore your site.

In Make Dynamic URLs Search Engine Friendly, the author steps you through a very simple process involving an htaccess file, and some calls to the RewriteEngine in Apache. From there, it's pretty much all magic. Instead of URLs like: foo.php?var1=this&var2=that&var3=crazy, you get nice, clean-looking URLs like: foo.php/this/that/crazy. Search engines eat this stuff up, and have no idea that it's not the "normal" URLs you're used to seeing all over the web.

PHPDeveloper.org currently uses something similar to this to get the URLs and links to sections, but, since it was a little bit more complex than just one format for all of the pages, we opted to go with a PHP-based solution. Either way can work wonders for your code and your site - making it not only simpler for the search engines to spider, but also to help your users remember the URLs to items much easier...