Mac: Need to just quickly play a song from you hard drive, but don't want to go through the trouble of opening up iTunes? OS X Daily points out that Spotlight's the best choice for doing so. While you've long been able to play songs from the Finder or with Quick Look, neither of those options can continue playing in the background. Spotlight can. Open up Spotlight (Command+Space), type the name of the song you want to play, then tap the play button in the middle of the album artwork. The song will play through until the end or until you manually pause it. It's a pretty good way to play a single song without dealing with iTunes.
Play a Song from Spotlight Search in Mac OS X [OS X Daily]