encyclopaedic author Ian Christe does an absolutely amazing job on his show "Bloody Roots" on the hard attack Metal station..... it is like a university course on the important history of heavy metal music and even those hardcore metal fans can learn something pretty much every show, and it is must listening for the newbs that like metal but maybe are younger or haven't learned all the roots and important influences...
the guy really knows his stuff
http://en.wikipedia.org/wiki/Ian_Christe