Ms. Kline Online

A podcast is an audio or video production that is produced and posted to the web regularly, to which users can subscribe via an RSS feed. Podcasts can be produced using Free software such as Audacity, or using commercial software such as Apple's GarageBand software. Video podcasts can be produced using a variety of Free or commercial video-editing software.

Read about podcasts in Wikipedia!

Audacity
Free audio editing software:
http://audacity.sourceforge.net/

Podcatchers
This is a list of free and commercially available podcatchers
http://en.wikipedia.org/wiki/List_of_podcatchers