Pandora.com has created an excellent series of music podcasts.
The topics created so far include:
    *  Up Next: Pedal Point
    * Drums and Drumming, Part II
    * Elements of Salsa
    * Recording Vocals
    * Electric Guitar Effects
    * Drums and Drumming, Part I
    * The Basics of Vocal Harmony
    * 2007 Pandora Podcast Schedule

Their 2007 schedule includes the following additions:
-Bass Guitar in Pop and Rock
-The Blues Scale
-Brass: Trumpets, Trombones, Tuba
-Common Chord Progressions
-Dissonance
-Country and Bluegrass, Yesterday and Today
-Drums and Drumming, Part Two: Swing
-Electric Guitar Effects
-Elements of Salsa
-Hip Hop Rhyme Schemes
-Holiday Music
-Jazz Improvisation
-M-ajor and Minor Tonality
-Meters and Time Signatures
-Mixing Vocals
-Pedal Point
-Pop Percussion
-Putting Words to Music, or Music to Words
-Recording Vocals
-Reggae, Rock Steady and Ska
-The Science of the Riff
-Strings
-Studio Sheen: Mixing and Mastering
-Singing Intervals
-Upright Bass, Bowed and Plucked
-Vintage Keyboards: Hammond, Rhodes, Moog
-Vocalizing: Range, Tone, Vibrato

http://blog.pandora.com/podcast/

Good stuff. Enjoy!

Max

some good info at this site