This might not be the answer you're looking for, but in Windows7, you can quickly mute all applications except specifically selected ones:
- Open the audio mixer.
- Mute the master volume (main speaker)
- Un-mute the volume control for the specific application you want to hear audio from.
This will have the effect you're looking for with any application that plays audio; the primary drawback is that when you're done, you'll need to manually un-mute all of the other applications in the mixer.