Sessions: APACHE HACK instead of -trans-sid?

I've heard the other alternative to PHP's --enable-trans-sid option is an Apache hack. I've seen it used on Amazon.com. It appends a unique ID at the end of your URL *ALWAYS*, at the Apache level, not the HTML/PHP level, and just knows to filter it out and process the other parts of the URL that it needs. My site is already doing something similar to this. And I own/run the server, and can hack-up Apache all I want. Does anyone know HOW to do it though, or perhaps direct me to a URL about what mod_rewrite-type thing I need? (I'm asking my PHP friends here, because you guys already know what --enable-trans-sid is...) Thanks!