I suggest The Metal Voice: reviews of good albums and pretty funny guys who also respond to you, they are metal veterans and can thus also share some interesting background information most of the time. The only downside to me seems they mostly only talk about the more well-known stuff you already know.
Another good channel is jumblejunkiemusic, quality reviews and a pretty funny dude too.
There used to be this absolutely great channel ran by some guy from Cairo, called Time Dilation Metal. He had lots of albums of the founding bands of the metal genre. Very awesome underground stuff, knew of alot of old school bands there. Yet some day, for some reason, YouTube terminated his channel AND account. FU YouTube...
Last edited by BFenix on Fri Sep 23, 2011 10:17 pm, edited 1 time in total.