I remember that I could do this by messing with input devices at the sound configuration menus, but it doesn't work anymore. I want to make the default input be a virtual mic that's the sound that's coming out of the speakers, while still being able to listen to it.
This solution allows you to record what you're hearing, but I don't know how to make it a default setting for anything. The instructions, updated for 11.10:
It seems that the gnome recorder defaults to that device afterwards, but I don't know if this persists across boots (or is indeed what you wanted).