Screenwriting : Screenwriting Contests by Ehab Moniem

The Nicholl Fellowship is the biggie; placing well there can be a major career boost. Also check out Blue Cat, and the Final Draft Big Break contests. Moviebytes has pretty much every contest on earth listed, and sortable by several different factors, including prize money and submitter reviews. I'd recommend that as a good starting point. Also, withoutabox.com has a pretty good submission system that's worth checking out. Hope that helps! I'm sure I missed a bunch of good options