So I'm surfing around the net this evening, digging through some URL's, and I come across a blog with some interesting information on it. Apparently, you can do a Google search for "index of /mp3" or "index of /files" and get all sorts of nice directory listings from some poor sap's personal stash.
In case you need a hyperlink to try it, try clicking here for the results of a search for "index of /mp3".
Also, try all sorts of other interesting filetypes... you'll never know what you might find!
"index of /mov" "index of /movies" "index of /mpg" "index of /files" "index of /warez" "index of /isos"
Lets not forget to make use of our friend wget. (man page)