Smashwords, Alfie Dog, Amazon.uk and Amazon.com. I think you'll recognise several of the author's names.
Here's a short story competition with a £1,000 prize. It doesn't say humour is required, but as they want children's stories, it probably won't hurt.
Bingo is a funny subject for poetry you might think. Win this competition and you'll have £150 to laugh about.
Update The finalists of the 100 word story competition I mentioned in my last post were announced this afternoon.