One of the few problems that Mac OS X Lion has is that you cannot control the volume of each application separately. A new Mac app called SoundBunny from Prosoft Engineering aims to solve this problem, giving you total control of the volume, app by app.
If you want to be listening to YouTube more than you want to be listening to any other sound your Mac makes, or if you’re recording or podcasting, and don’t need to hear the various beeps and pings that many programs make from time to time, you can temporarily (or permanently) adjust the volume by muting the offending apps.
This is a pretty awesome little app. What’s more, it’s only $9.99, and you can test drive it for 30 days before you purchase. My advice, however, is that it’s well worth the $10.