Alan Weiss just recently presented a wonderful 7-minute podcast on "Creating a great speech". You can find it and others in his series at: http://www.contrarianconsulting.com/category/podcast-series-the-way-i-see-it/
What is a podcast? It’s just an audio file you can play on your computer. You also can download it, save it, and listen to it later on. Then you can move it over to a portable MP3 player (iPod, etc.) and listen while you jog or drive.
UCLA has an introduction called "What is Podcasting?" that you can either read one chunk at a time or download as a big .pdf file to read later. See http://www.oid.ucla.edu/units/tec/tectutorials/casting/whatispodcasting01