wheel - 5:25 pm on Jan 30, 2006 (gmt 0)

This is probably more than you need or are looking for, but what I do is set up apache to have the 404 page go to a script. That script then does a lookup in a mysql database that maps the 'pretty' url to the dynamic url. If it finds the pretty url in the database, it issues a 200 page header and then displays the page. If it doesn't, it leaves the 404 and displays an error.

That allows me to map pages without any consideration for patterns or regular expressions in the URL's. What it doesn't do is map a dynamic page to another dynamic page.