[5xz41s0P8T5N]

OS X: Audio Hijack (USD 32) http://www.rogueamoeba.com/audiohijackpro/buy.php

[dfc]

Save $32:

  apt-get install jackd2

[getsat]

You mean:

  brew install jack

[dfc]

Haha. Definitely not for me, but you are correct given the impetus brew is more apropos.

[cowmix]

Or SoundFlower for OSX:

http://code.google.com/p/soundflower/