UPDATE July 6, 2012: Now there is a grandson, I now run my setup through Ladiocast, which offers much more mixing capability and manages the use of Skype as a source- see http://cogdogblog.com/2012/07/06/rube-goldberg-broadcast-machine/
Lots of people seem to have gotten a start on ds106 radio broadcasting using Nicecast on Mac OSX and my first guide to niceasting. Since then, I’ve been modifying my method a bit, so it seemed time to update.
As always, your first point of entry into anything related to ds106 radio is the shared doc at http://bit.ly/radio4life which covers info about the radio, how to listen, and how to broadcast.
The setup I described the first tome around works well for the scenario of wanting to slide between your voice and audio from an application, e.g. DJing music from iTunes. This would not work, however, if you wanted to use say 2 audio apps, or if you wanted to do, say a Skype call-in show (which has been tutorialized elsewhere using SoundFlower, and/or audio mixing apps. There always seems to be a lot of audi source switching to do this, but of course its possible.
This all started with a little fun last week, when jim Groom was clamoring for the stream from his visit to Cole Camplese Penn State, but never seemed to pick it up. I thought it would be fun to tease him, and grabbed the stream, with a set up of using QuickTime Player as my source. I found that by opening several clips in the player, setting them to Loop, I could get some interesting skips just by activating the player- each time I made another window active, it became the audio source. Most fun was playing the “Rowan Peter / Peter Rowan” clip again and again.

If you really want to hear this deviance, I got it:
Jim Groom Radio Lockout