This is the channel that i spend most of my IRC time at, the site is actually Stonerrock Mailing Lists users pics site, but the bottom of the page has WebChat thingy. Stonerrock Rogues Gallery If you use mIRC etc, just go to an UnderNet server and join #Stonerrock. On this channel I'm an OP, I'm the ever blabbing guy with the nick Shrike. You can also try #Stonerrock for it, this is more 'official' and 'related to the IRC only' site. Here is a place where you can check the channels users mugshots and here you can check out the channels talker stats.
This channel is another one of my favourites, Doom-Metal.Com has more to it that just an IRC, but once getting in just click "Chatting (IRC)" and you'll see the IRC stuff, where I'm listed as an regular. In UnderNet too.
This channel is yet another one of my favourites, #Metal is in IRCNet, their site has all kinds of stuff, mostly IRC related tho. I'm listed as a regular here too. There is also a Finnish one called #Metal.Fi in there.