What is a Podcast? According to Wikipedia...
A podcast is a digital media file, or a related collection of such files, which is distributed over the Internet using syndication feeds for playback on portable media players and personal computers. The term, like "radio", can refer either to the content itself or to the method by which it is syndicated; the latter is also termed podcasting. The host or author of a podcast is often called a podcaster.

The term "podcast" is a portmanteau of the words "iPod" and "broadcast", the Apple iPod being the brand of portable media player for which the first podcasting scripts were developed (see history of podcasting). These scripts allow podcasts to be automatically transferred to a mobile device after they are downloaded.

Though podcasters' web sites may also offer direct download or streaming of their content, a podcast is distinguished from other digital media formats by its ability to be syndicated, subscribed to, and downloaded automatically when new content is added, using an aggregator or feed reader capable of reading feed formats such as RSS or Atom.

The Instructional Technology Department of Knox County Schools has a number of podcasts available for teachers:

TCs'NaPod- A collection of podcasts designed to help teachers help themselves with everyday technology problems.

TIME for Teachers: Technology Integration Made Easy-
A collection of integration ideas for teachers by teachers.

Hotlist of Science Podcasts!

Podcasting News: Science Podcasts
http://www.podcastingnews.com/forum/link_17.htm

Vivisimo Science Podcasts Results
http://vivisimo.com/search?tb=vivisimocom&query=science+podcast&x=0&y=0

Links to Podcast Websites

AAAS Science Magazine Podcast
http://www.sciencemag.org/about/podcast.dtl

Berkeley Groks Science
http://www.ocf.berkeley.edu/~clgroks/podcast.html

The Naked Scientists
http://www.thenakedscientists.com/HTML/podcasts/

Nasa Podcast
http://science.nasa.gov/podcast.htm

NPR Science Friday
http://www.sciencefriday.com/audio/

Our Ocean World Daily Podcast
http://www.ouroceanworld.com/2001/oceanworld.htm

A few titles available at iTunes (Most are enhanced with Video)

Feature providers for iTunes include: PBS, NASA, Discovery Networks, Scientific American, NPR, ABC Radio National, Green.TV, CBS and SOH Radio