Independent Book Publishers Association runs this one. Im a member, but dont get any dough for recommending them. The cost is $190 for non-members (which includes one year membership to IBPA). While there is no cash prize, the competition has a lot of cred. Its been around for 25 years.
Writers Digest has a pretty good rep as a place for authors to find useful advice and tools/services.
All the contests except the Your Story writing contest cost something, but not more than $100. Prizes include cash, up to $3000.
Writers Digest Annual Writing Competition (their catch-all contest which allows almost everyone to enter)
Self-Published Book Awards
Sci-Fi Book Awards
Thriller Book Awards
Young Adult Book Awards
Romance Book Awards
Crime Book Awards
Horror Book Awards
Your story (this one is free and the winners 750 word story is published in their magazine)
Yeah, heard of them? Their annual self-published writing competition is becoming the king of writing contests. Entry is free and super-easy. Winners get $15-50,000 cash, a publishing deal and exposure on Amazon (yes, cash and exposure on Amazon is redundant).
These guys have been around forever. Lots of cred, a little on the stuffy side, and a nice, big deal if you place in the competition. The cash prizes are up to $10,000 They have $125 fee per submission. Dont pay it until they invoice you! Seriously, its in the fine print.