I'm not sure if it can be considered a cult movie but it is a classic for sure. I've only seen it only a couple of times but I dig it. Hopper, Fonda, Nicholson, Black...can't go wrong in my opinion. I've read that the actors actually smoked pot but the cocaine was fake. I've also read that Hopper was difficult to work with and was paranoid the whole time.
I think it fits the definition of cult too I saw another active thread on here about Easy rider not too long ago. Maybe fun to check out and join in there!