I want to do this one day, but have no plans of doing it any time soon: a playlist generator for different sized mp3 players. An app I install locally that will scan my music library and then I select a song and the app mashes up with last.fm and generates a playlist of the best similar songs that I currently have that is a maximum total size in MB so all I have to do is put that playlist into whatever I transfer my music to mp3 player with and everythings done. Easy way to fill up my mp3 player with fresh music every day.