Out of the over 50,000 apps in the App Store, MacWorld magazine picked Concert Vault as the best app of 2009. This free app lets you enter in your favorite band or artist, and then you can listen via streaming audio to an actual concert that was recorded sometime in the past — U2, early Bruce Springsteen, Janis Joplin. The collection spans the 1960s through today. Obviously not every band or artist will be represented, and the current ones less so. But hopefully you'll find something you'll like from among the thousands of concerts. The service does require e-mail registration.