Audio Hijack Pro is awesome if you need its fantastic array of tech geegaws but it's too complicated and hard to use and more expensive for most people who just want to record the audio on their computer (e.g. skype) methinks.
It's true that I don't know an awful lot about podcasting, but Peter Rees pointed me at this article.
Reading it sounded like a really complicated way of doing something simple. There was even a comment about doing this on the Mac. Here I would play with Audio Hijack as a way of capturing the conversation. Although the article is some what old, I like the idea of capturing a skype call as an interview, that I hadn't considered.