Coming on the heals of my "why the Twilight movies suck" post, I found this article on Stephanie Meyer's website. It is from 2007 when they first decided to make a movie and before anyone was ever cast. Stephanie goes into who she imagines for each roll in her best-case-scenario. She includes pictures and everything!
You will note that on her list of Edward suggestions is Jackson Rathbone, who plays Jasper (and looking much better with his real hair than that ridiculous blond one he wears). I've been telling people that he would have made a better Edward than Robert. Apparently he auditioned for Edward, but didn't get the part. boo!
Also note that Stephanie makes the point (several times) that she had NO SAY in who was cast. I think she should have had some say, but I'm guessing no one knew how big this would be. If she had known, she could have held out for some control.