Podcast From Space? Not Yet.
NASA - Steve Robinson: First Podcaster From Space
I don't mean to diminish the importance of STS-114 with this comment: the linked article merely references a downloadable MP3 recording. A key element of podcasting is syndication via RSS enclosures. A quick scan of NASA's RSS feeds doesn't reveal that this was syndicated content. This is the only NASA podcast feed I've found.
I'm just picky, I guess.
Please arrive home safely, Discovery.