Detour for Mac

Detour lets you control where audio from all your programs is going by allowing you to send audio to different output devices on an application-specific basis. This means you can...

...send music from iTunes to your external speakers and keep the annoying beeps and blips of iChat going through your computer's built-in speaker.

...mute any application's sounds all together.

...change the volume of some applications relative to others. Make your email client's alerts quieter, and you'll never again be jarred from work just to receive spam.