AirServer allows your computer to show itself as an Airplay speaker to compatible devices, which might seem silly or unnecessary to some, but its actually pretty neat, especially if you think of iOS music apps.
Say you have good speakers hooked up to your computer, and want to stream an iOS app such as Spin Play, Aweditorium or Woodstock to good speakers. You could tether your iDevice to those speakers, I suppose. Or you could just push the audio from said iDevice to your computer, and save yourself the trouble. And at $US3, the AirServer seems like a cheap multi-room audio solution. [AirServer via Wired]