Oxy/H grade nod - Pink Floyd's Dark Side of the Moon, or Kind of Blue by Miles Davis. Santana's Caravanserai. And oddly enough anything by Pinback. On opiates my first choice is always something a little jazzy, or layered... but I do love the hell out of some Alice in Chains, Nirvana, Chili Peppers, Sublime, Pixies, Radiohead, The Mars Volta...
Super stoned on cannabis I always go back to Led Zeppelin, the Beatles, Velvet Underground. Or some hip hop.
Amphetamines/MDMA I love RATM and Incubus, TV On the Radio and Portugal. The Man.