Kae Verens has posted a quick tutorial about serving up files by routing them through a "fetch" script, pulling their contents in one side and back out the other.

One thing I need to do while building the multi-user version of webme is to convert it so file references such as /f/photos/an_image.jpg get transparently converted so they serve correctly, even though the actual file may be located somewhere entirely else.

There's two steps involved - rewriting the URL request for the types of files you'd like to pull through the script (using some mod_rewrite magic in Apache) and make the script to do the actual work. Source for that is included too. Not only can something like this help you keep things organized but it also allows for extra security if you need to store the files outside of the webserver's document root.