A few contests going on:

Amazon Breakthrough Novel now has a YA category: http://www.amazon.com/Breakthrough-Novel-Award-Books/b?ie=UTF8&node=332264011

KidLit blog (sorry, this one ends today, but she often has contests going on): http://kidlit.com/kidlit-contest/

Sourcebooks contest: http://teenfire.ning.com/

And, associated with that is a really cool YA ning community where they talk all YA happenings and they’ll help you with your ms’s: http://yalitchat.ning.com/