Actually I went on wikipedia.org, I believe to get the jest of it. I also looked up reviews online to see what was really going on. I think most of the movie was a dream and then he got crushed by the jet engine or something.....but I'm sure the naysayers will correct.

ok i thought he was schizophrenic. and the whole ending was what if he had never existed? or more like donnie darko was his own delusion

I havent seen S. Darko and don't care to because there's no way to feasibly sontinue the story. Basically in a simple terms as I can put it (which is gonna be hard because D. Darko is a very complicated story is about what happens when time/space anomolies occur. Basically a Tangent Universe spins off of the Primary Universe, signified by the appearance of an Artifact; here represented by a jet engine. Tangent Universes are inherently unstable and will collapse in less than a month, taking the Primary Universe with it, if not closed off. Closing the Tangent Universe is the duty of the Living Receiver (Donnie), given super powers to perform this task. Those who die within the Tangent Universe are the Manipulated Dead (Frank and, according to the back of the book, Gretchen) who are also given certain powers, understanding of what is going on, and the ability to contact the Living Receiver via the Fourth Dimensional Construct (water). Everyone else in the orbit of the Living Receiver are the Manipulated Living, who are subconsciously drawn to push and prod the Living Receiver towards his destiny, closing the Tangent Universe and, apparently, dying by the Artifact. A very clever story about time travel, wormholes, tangent universes and other anomolies and theories....though the film somewhat leaves open the slim possibility that the event was a daydream, dream, hallucination, reverie of Donnie or his mother, that's a bit of a simple answer copout and not really the point of the film. But basically the tangent universe was destoryed and everyone within it, those int he other universe experienced nothing, only the death of donnie, so the universal anomoly was corrected, the odds of it happening again are probably astronomical, so I see no point for a second or third film which would probably only bastardize the original concept of the film.

Why not check it out here: http://www.imdb.com/title/tt0246578/

All the answers and comments I've found helpful here - thanks! Proves that mgl's question is a darn good one! [ I really liked Donnie Darko despite not understanding it at all. :) ]