The "Official" HM site: http://www.heavymetal.com/
John Findley's Tex Arcana was one of my favorite HM stories. He has it all online, with some edits, and for sale as well, and a fourth book in process. Not updated frequently (it's been a couple years) but still really cool: http://www.texarcana.com/
Rod Kierkegaard Jr. did Rock Opera in the 80s, which not everyone liked but I did. He's still writing, his Obama Jones and the Logic Bomb is futuristic and very enjoyable, you should read it. And his other stuff too. His blog hasn't been updated in a few years: http://rodkierkegaard.blogspot.com/ but he's more active on twitter these days: twitter.com/rodkierkegaard
heavymetalmagazine.tumblr.com/ a now-comic-artist putting up a scan a day of HM pages, from his late father's collection, with a critical but appreciative eye.