Skype: How to record a podcast?
Use CallGraph. It is free and easy to use. Plus you can configure it to record the two halves of the conversation on different channels (left and right) which makes editing easier. They have actually had very responsive support (free) when I have had questions too.
Pamela is a little better, but more expensive, unless you only want to record really short pieces.
Update: I've actually switched to Pamela Professional now. I was having some odd sound quality issues with CallGraph and their support (yes, a free program with actual support) wasn't able to help me resolve it. Pamela has its own problems though, like occasionally not recording anything.
Audacity should do the job
See:
- Record a phone conversation with Skype
- Recording Skype call - can you help?