Mac: You have a have a surprising amount of choices if you want to control iTunes from your menubar, but Muzzy takes a decidedly simplistic approach to give you access to just the things that matter: tracks, lyrics, time and notifications.
Muzzy quietly sits in your menu bar and doesn't get in the way unless you want it to. When you're playing tracks in iTunes, just click Muzzy to get access to album artwork, lyrics, a scrubber, Last.fm integration and more. Muzzy also has the iPhone-like ability to automatically pause the music when you disconnect your headphones. Muzzy isn't exactly feature-packed, but it's free and does plenty.