Podcast – an audio show that is released or distributed via an rss feed
Rss feed – an easy to create document that contains the locations of the files, their file size, and any show notes you’d like to release
Aggregator – a bit of software that checks the server for new podcasts, downloads them, and some will play the corresponding audio files

Software
Audacity - cross platform
Cast Blaster - 50 dollars. Mixes on the fly, allows for 6 preloaded songs and 6 preloaded sound effects, will upload and tag your podcast for you.

Website/Feed Software
Wordpress – blogging software
Feedburner – formatting your feed

Podcasts Networks
Podcast Pickle - general list
iPodder - general list
Podcast Alley - general list
iTunes - general list
PodioBooks – audiobooks
Star Wars Fanworks – Star Wars list
The Sci-Fi Podcast Network – general sci-fi
The Bat Feed – general comics/sequential art
DragonPage.com – lots of sci-fi goodness

Shows
Radio Adventures of Doctor Floyd – comedic serial
Campfire Tales - stories
Amazing Pulp Adventures staring Mister Adventure
Governor Schwarzenegger's California Minute

Aggregators, Clients, or Podcatchers
Doppler
IPodderX
iTunes
FireAnt