Podcasting is a combination of the words:
[i]Pod (the Apple mp3 and mp4 media device) + [broad]casting. However, podcasting describes audio and video segments that are not broadcasted live on the web, but can be accessed on demand. Podcasts can be downloaded to any mp3/mp4 media player and listened to anytime anywhere, downloaded to the computer or listened to/viewed online.
So what is the difference between a podcast and other media files on the web?
Podcasts can easily be traced using a feed aggregator or feed reader. According to Wikipedia,
"aggregators reduce the time and effort needed to regularly check websites for updates, creating a unique information space or "personal newspaper." Once subscribed to a feed, an aggregator is able to check for new content at user-determined intervals and retrieve the update. The content is sometimes described as being "pulled" to the subscriber, as opposed to "pushed" with email or IM. Unlike recipients of some "pushed" information, the aggregator user can easily unsubscribe from a feed.
The idea behind podcasts is that the content is frequently updated and the audience can have easy access to them by downloading the most recent or useful feed items (aka files) using a simple podcast reader. So, in comparison to any other audio or video files on the web, podcasts need to be in either mp3 or mp4/m4p format and be frequently updated."
Can I reuse existing files as podcasts?
Any existing audio or video file converted to mp3 or mp4 format can be used for podcasting. So, if you already have a bank of media files in various formats, then you can start converting them using one of the many mp3 converters found online.
IMPALA project: Informal Mobile Podcasting and Learning Adaptation
Sounds Good JISC project(Audio Feedback)
TechDis Podcasting and Accessibility
Audacity: Audio Recording and Editing Software