I think A Gift From Earth by Larry Niven would make a really outstanding movie. Great plot, and doable to boot. I know Moot mentioned Snow Crash and the Diamond Age, both of which were really excellent also, and could make great movies.
I have always been a huge Phillip K Dick fan also, and have been horrified to see how badly his books and short stories have been butchered by Hollywood. With the exception of A Scanner Darkly, which was excellent and follow the book pretty well, and Blade Runner (Do Androids Dream of Electric Sheep) which was slaughtered and flawed, but still an excellent movie, all of the movies made of his stuff has been pretty crappy and far from the ideas behind his works.
I think Ender's Game by Orson Scott Card would make as great a movie as it is a book also! It might be hard to get enough kids to pull off the level of acting that it would require though.
There are tons more, SciFi is some of the most creative storytelling going when it's at its best.