The Heinlein Society has announced the Robert A. Heinlein Centennial Short Story Contest, with prizes of $5,000, $2,000, and $1,000 given "for the best original short stories reflecting the spirit, ideas, and philosophies of Robert Anson Heinlein." There is no entry fee and the deadline is June 1, 2008. More information available on their website. Needless to say, I imagine they'll receive quite a few submssions in the next eight months.