I'll second the Evil Dead movies.
Dusk 'til Dawn,
Blade (all 3),
Matrix (all 3),
Clockwork Orange,
Both Bluesbrothers,
Star Wars (all)
Star Trek 2, Wrath of Khan
Clockwork Orange (seems real popular here, sure it qualifies?)
Harold and Maud (I still want that hurse, what a thing of beauty)
Pitch Black (I know, but I saw it back when nobody had heard of it, really)
pi (except that one was really more of a documentary cause it was all real)
the list could go on....
Run, run, run, as fast as you can...
you can't catch me, I'm the Stinky Cheese Man.
Evil Dead One
Dawn of the Deads (old, AND new I guess)
Donnie Darko
Night of the Living Dead's... theres quite a few
Cube
HyperCube
Cube Zero........with those three watch em in the order I posted
Many more, it really just is to the extent of what you want to classify "Cult Movie" as..... Becuase come on Napolean Dynamite.... no thats not a CULT Classic.... and many more other people listed are not cult classics..... but whatever.