It is really a very simple process of downloading and installing Soundflower (a free audio utility) and LineIn (another free audio app). First you must enable Soundflower (ch2) as the audio input and output of Skype. This is done within the audio preference pane in preferences (accessed via the Skype menu). Then on must select Soundflower (ch2) as the input for GarageBand (make sure to lead the output as built in audio). Next, you must then enable your mic (built in, audio line in, or audio interface) as the Input in the LineIn Application. The output should be set as Soundflower (ch2).The system preferences should remain with built in audio for output, and whatever input you are using (built in or otherwise) to record properly. There is also a Pass Thru button you enable in LineIn.
Once you have the correct settings, you should then have no trouble tracking live audio of your Skype conversations. With GarageBand's convenient editing and publishing features you should have no trouble uploading a podcast or creating a mp3 archive. If you have latency issues (developing an echo or delay), select minimum delay when playing instruments live (small buffer size) in the Audio/Midi settings. These utilities should function with most other sound recording software for Apple Mac, assuming it has editable settings.