Hey there! Owing to current issues affecting Twitter, only direct messages are currently being read. We'll let you know when you can use @replies again, but for the moment, stick to DMs. Sorry about that.
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