Podcasts were originally audio, many are now video (some are called webcasts). Many series offer subscriptions and most sites offer the choice of listening immediately or downloading for your own future use from your computer or portable player (e.g. iPod, tablet).
- apple.com/itunes/podcasts
Tips and indexes - npr.org/rss/podcast
Assorted podcasts or build your own - podcast.com
Extensive, indexed in 16 categories - loc.gov
Podcasts created by Library of Congress - scientificamerican.com/podcasts
Science Talk and 60-second Science in podcasts - www2c.cdc.gov/podcasts
Center for Disease Control podcasts