trendalicious is a real-time ranking of the 100 most popular web pages as reflected by del.icio.us, digg, and reddit. URLs posted to those sites are collected and ranked by their total number of votes or links.
In a recent update - Bookmarked items in del.icio.us that end in one of a number of filetypes will now automatically get some system tags added. You can use these just like normal tags. So if you are looking for mp3 files - See the system:filetype:mp3 tag