On CodeSnipers.com today, Peter Harkins talks about a method, using regular expressions and Apache to turn ugly, GET-laden URLs in your application into clean, search engine friendly URLs without altering the underlying scripts.
So we have two goals. First, requests for the new URL are internally rewritten to call the existing scripts without users ever knowing they exist. Second, requests for the old URLs get a 301 redirect to the new URLs so that search engines and good bookmarks immediately switch to the new URLs.
He starts with a sample .htaccess file, showing a simple RewriteRule to take in the request and remap them back to the old PHP script's input format. They work through a few more changes, noting issues along the way (in case you hit them too) and end up with a simple, and much easier way to achieve clean URL bliss.