A podcast is a multimedia file distributed over the Internet using syndicationfeeds, for playback on mobile devices and personal computers. The term, as originally coined by Ben Hammersley in an article in The GuardianFebruary 12, 2004[1], was meant as a portmanteau of "broadcasting" and "iPod".[2] Like 'radio', it can mean both the content and the method of delivery; the latter may also be termed podcasting. The host or author of a podcast is often called a podcaster.

Though podcasters' web sites may also offer direct download or streaming of their content, a podcast is distinguished from other digital audio formats by its ability to be downloaded automatically using software capable of reading feed formats such as RSS or Atom.

See more:  http://en.wikipedia.org/wiki/Podcast 

News on Podcasting:   http://www.podcastingnews.com

MMS casting:              http://www.geocities.com/tvhuangsg/mmspodcast

Videopodcasting:         http://www.videopodcastingnews.com