For a good summary about how other people do it see How we do our home work which documents how the Home Work podcast gets recorded and post-processed:
- QuickTime for audio recording
- GarageBand for audio editing
- Levelator
- Sound Studio to adjust the sample rate, mix down to mono and add metadata
Depending on your setup and your quality requirements you can at least combine #1 and #2 by recording directly in GarageBand and also add intro/outro parts.