If you write sci-fi or fantasy then this competition could win you up to $6,000. The same amount is on offer for illustrators. You won't earn so much for this one, but the winner will be paid and there's a trophy.
Can't remember if I mentioned this before (but better twice than not at all) $500 prize and a trophy.
Not a competition as such (but submitting anywhere is a competitive business) this is a paying market you might like to try.
Winning one of these books might be useful for research or just for procrastination.
Jinx Schwartz's the Texicans is free 20th - 22nd December.