Oh boy. List time of bands I listen to/love:
Ahab--Funeral Doom (in the vein of Evoken)
Alcest--Shoegazer/progressive and black metal
Anaal Nathrakh--Extreme black/death metal
Ataraxie--doom metal with black metal influences.
[b.abuse]--instrumental doom/atmospheric
Baroness--prog metal
Black Shape of Nexus--ambient doom
BLCKWVS--instrumental atmospheric sludge.
Boris--sludge, doom, drone, hardcore, punk, ambient/atmospheric. Mostly doom, drone, and sludge.
Buried at Sea--funeral doom, but a bit harsher, slightly more droney, and more black metal inspired vocals.
Cynic--avant-garde/progressive metal
Doomshine--epic doom
Earth--atmospheric drone metal
Envy--Japanese hardcore band.
Evoken--funeral doom. One of the first big bans to do funeral doom.
Funeral--funeral doom (surprise!) with clean vocals.
Greg(o)rian--progressive-ish; really long songs.
Isis--post-metal, progressive, avant-garde.
Iwrestledabearonce--speed/thrash, I think. Not sure what they get labeled as.
Khanate--um...blackened atmospheric doom? Really long, painfully slow songs that are really depressing.
Jesu--progressive, usually melodic metal.
Leviathan--black metal
Mastodon--progressive.
Maudlin of the Well--avant-garde.
Motograter--thrash/nu-metal.
Mourning Beloveth--some awesome Irish doom metal.
Mouth of the Architect--atmospheric semi-melodic sludge is the best term I have.
Mushroomhead--alternative metal. Awesome if you're into more normal stuff.
Neurosis--progressive, avant-garde, some thrash/hardcore pieces.
Ocean--funeral doom.
The Ocean (different from Ocean)--progressive/avant-garde metal.
Ophis--funeral doom metal
PainForged--most of what I've heard is a cross between drone, atmospheric and funeral doom.
Pelican--instrumental metal
P.H.O.B.O.S.--uh...blackened atmospheric industrial doom?
Rammstein--NDH/tanz-metal. Very melodic heavy metal with clean vocals.
Rigor Sardonicous--very slow funeral doom with more distortion/filters than most bands ever think about using.
Rosetta--semi-atmospheric post-metal. Their lyrics are some of the best.
Sabazius--drone (all their stuff is free online!)
Sinistra--drone-doom
Sunn O)))--gods of drone/dark ambient.
Swallow the Sun--Finnish metal group. Not sure if they're prog metal or what though.
Teeth of Lions Rule the Divine--drone
Tephra--post-metal/doom/ambient
Thergothon--fathers of funeral doom. Slow songs, deep growled vocals.
Tool--technical prog/avant-garde.
Xasthur--atmospheric black metal
Zaraza--industrial doom.
Ариа (Aria)--more traditional heavy metal, from Russia. Like Iron Maiden but I think better.
I'm sure I'm forgetting a few. That list is very representative, though, covering basically all the metal I listen to frequently. It ought to appeal to those of a more eclectic taste (i.e., metal hipsters, snark snark snark) or who prefer longer, slower, more atmospheric pieces.