ChapterToolMe is a nice GUI for the Apple ChapterTool utility to make simply chaptered AAC file for your podcast.
flipflip's podcast downloader
flipflip's podcast downloader is a script that downloads podcasts. Is has options to limit the number of podcasts to download, to rename the downloaded files based on rules, and to tag the MP3 files with custom content or with content derived from the feed metadata. The program is very small and has very few dependencies (id3v2 and wget).
localcast is designed for Mac users who want to be able to resume podcast downloads after an error or unexpected sleep, something that iTunes cannot do by itself. It depends on Mac OS X personal Web sharing and on wget. With localcast, interrupted downloads can be resumed, because wget fetches the podcasts. Podcasts appear fully integrated in iTunes just as if localcast was not in use.
(commercial) Videator lets you make your own movies and podcasts. You can take snapshots, add realtime effects, mix music/sounds/midi, and edit existing movies non-destructively.
Xcast is a free, simple, yet powerful Podcast client with unique features like full integration with the iTunes Podcasts section, smart relocation of downloaded enclosures, iTunes Podcasts cleaner, and more.