Major Kong comes highly recommended by several sources as some great sludge metal. This is down and dirty instrumental doom metal, I can't really call it sludge, because to me sludge is all in the vocals, but I feel I'm just splitting hairs there. The songs (four of them) are long and drawn-out, seeming to go on forever.
Orogenesis (available for free download), the debut EP from the guys of Fifty Foot Woman, is for anyone who loves some dark doom. If you're looking for complex rhythms or styles, you need to be listening to something else. The songs are droning and fairly predictable, but at the same time, they will melt your face (which would be a sweet album name).