OK, this is my new favorite thread.
First off, the obvious. Witness the holy trinity of stoner:
Black Sabbath
Sleep
Kyuss
Other essentials (These definitely don't all fit into the same genre, and there's a lot of overlap, so I devised a legend):
#=doom, %=psychedelic, $=post-rock, @=drone, &=good old stoner riff rock
Electric Wizard (#####)
Orange Goblin (#%&&&)
Melvins (####&)
OM (##@&&)
Colour Haze (#%%%&)
High On Fire (###&&)
Earth (##@@@)
Bongripper (###$@)
Monster Magnet (%%&&&)
Cathedral (###&&)
Boris (#%$@&)
Fu Manchu (&&&&&)
Witch (##%&&)
Nebula (%%&&&)
Mammatus (%%%$&)
ISIS (##$$$)
Pelican (##$$$)
Nadja (#$@@@)
Jesu (#$@@@)
Karma to Burn (##&&&)
Bardo Pond (%%$$@)
Witchcraft (###&&)
Dead Meadow (%%%%&)
Yawning Man (%%%$&)
Pharaoh Overlord (%%%@@)
The Atomic Bitchwax (%&&&&)
Beaver (%&&&&)
Acid King (##%%&)
35007 (%%$$@)
Monkey3 (%%$$@)
Comets on Fire (%%&&&)
Grand Magus (###&&)
Eternal Elysium (##%%&)
The Sword (###&&)
UfoMammut (###@@)
Hermano (&&&&&)
Bongzilla (####&)
Dozer (##&&&)
OK, that turned out a lot more cryptic than I wanted it to, so if you prefer I can replace the weird symbols with a blurb about each one. This is my kind of music.
Stonerrock.com is your Mecca.