I stumbled across this "course" in iTunesU called Jazz Insights from Georgia State University, narrated by Dr. Gordon Vernick. Now this is not your typical iTunesU course.
The majority of courses in iTunes there are raw recordings of class lectures, where there is an assumed audience, and often writing on the whiteboard which you can't see.
However Dr. Vernick recorded these 15 minute clips specifically for the ipod listener to teach you about the grassroots of almost every aspect of jazz that you can probably think of. The quality of the recording is crystal clear, and he intersperses his comments with examples of music to demonstrate styles and techniques. Vernick's voice manner has the wonderful laid back "jazzy" quality to it that gets you in the mood. mmmmmm!
However, be forewarned that these are lectures recorded intentionally for the ipod. There's no really dumbing down of the terms used. But the language is accessible enough for anyone to understand, so don't worry. If you are a good student, and listen intently, I guarantee, you will KNOW JAZZ!
My favorites so far is the early years of Bill Evans, and his 4 part discussion on Oscar Peterson -- my all-time favorite jazz pianist. After all, I'm a pianist too! Thanks to Dr. Vernick for efforts in sharing his wealth of knowledge! I'm a fan!