In this podcast, Alex Hall demonstrates the use of Audio Hijack. This Mac app allows you to record audio from individual apps, the entire system, or any internal or external microphones you have. Better still, it can mix them together, apply effects, adjust volumes, live monitor, and more. If you do podcasts or anything else that requires recording more than one audio source at once, you can't go wrong with this app. It's also fully accessible, as talked about in its page on AppleVis itself.
To take full advantage of this app, there are a few concepts you need to understand, and those are what this podcast covers. It isn't a complete walkthrough of Audio Hijack, but rather a demonstration of the trickier parts that would confuse most users. You can also read this textual guide to Audio Hijack, which covers the same things as this podcast.
If you run into problems, leave a comment below, or ask Rogue Amoeba on Twitter.