I have to start spending more time reading through the market archives over at Ralan.com; I'm always finding marvelous sub ops there. For example, L. Ron Hubbard's Writers of the Future Contest. This one awards sizeable cash prizes for SF or Fantasy short stories up to 17K in length. So why is this so marvelous? Let me count the ways:
1) It's not open to professional or published writers. Only those who haven't yet published can enter (publication is defined by the contest rules as follows: "The Contest is open only to those who have not professionally published a novel or short novel, or more than one novelette, or more than three short stories, in any medium. Professional publication is deemed to be payment, and at least 5,000 copies, or 5,000 hits.)
2) There's no entry fee. Zero. Zip. Zilch. Which makes it completely affordable for anyone.
3) Entrants retain all pub rights to their work, which means if you win the contest you can still sell the story elsewhere whenever you like.
4) Editors, agents, or any other non-writers are not part of the judging process; the awards are adjudicated by professional writers. Aka your peers.
5) The awards: First Prize of $1,000, a Second Prize of $750, and a Third Prize of $500, in U.S. dollars or the recipient's locally equivalent amount.
6) You can submit your story in hard copy by snail mail or electronically.
7) The contest runs four times per year, beginning on October 1, January 1, April 1 and July 1. The year will end on September 30. The four first-place prize winners are then rejudged and one is awarded the grand prize of $5000.00.
This quarter's contest opened on April 1st and runs through until June 30th, so if you want to enter but have nothing written you have time to put something together. To get more details on submission requirements, check out the contest page here.