Editing your recorded media for a podcast is no different than editing an audio or video file for use on a web page. Depending on your needs, you may be able to cut and paste pieces of your recording using audacity or quicktime pro, or you might want a more powerful solution like GarageBand that allows you to create jingles and add in stingers, duck the background audio under the dialog and sync this all to a video or slideshow. There is an excellent online tutorial covering how to edit podcast recordings in garageband