I'm partial to Skip Tunes for controlling music on my Mac. It places playback controls in the menu bar and works with iTunes, Spotify, and Rdio. Skip Tunes costs $2.99, so if you are looking for a free way to control your music, check out MiniPlayer for Mac.
If you have a jailbroken iOS iPhone, you might be familiar with MiniPlayer. A jailbreak tweak, it has now been ported over to OS X. It's available for download at the developer's site; he has not submitted it to the Mac App Store because he wants to leave it open for other developers to create plug-ins for it; it appears nobody has done so at the present.
MiniPlayer for Mac supplies a small, floating music player and supports the same three services as Skip Tunes --iTunes, Spotify, and Rdio. You can choose which service to use from the Music Services menu option. The player features a simple layout, with play/pause and skip forward and back buttons. Click on the album artwork to bring up sharing options that include Facebook and Twitter.
MiniPlayer for Mac also includes search functionality, but the only results it returns are tracks. I could not find a way to search for an album. After using the app for the better part of a workday, I found it more useful to check the name of the track currently playing and skip to the next track, while I'd use Spotify itself -- my preferred music service -- to search for music to play.