Last.fm, I have an audio scrobbler that keeps tracks which 'tracks' I've been listening to. Kinda geeky, I know, but I still think its neat.
"Scrobbling" is a feature which keeps tracks are being played. Like mentioned before, it tracks anything I play on my computer, iPhone or iPad! Not necessarily in real time, but it will eventually get synchronized with my Last.fm account at some point. You've probably noticed that I've written about Last.fm before, utilizing some Wordpress and other website plugins, but these days I am just using it to "track" my tracks played. Now you can still see what I've got spinning on my player at any time by clicking HERE! You can also join Last.fm and become music buddies; so we can each check out what we're both listening to.
NOTE: If you see Justing Bieber and other "pop' tunes on my list of top 10 tracks being played, its not me! (its for my boys and general party-vibe music... ;)