The last time I wrote for a contest, I was in high school (won by the way). And the rate I'm going with Venus I'm going to be too old to enter it in a contest by the time I'm done with it. (I did pick up some research books this weekend, but haven't had a chance to read through them much)
I've always thought of writing contests as something that you do when you're first starting writing in your teens. Write a couple short stories, some poems, ship them off and see what the world in general thinks of your style. If you hear back, great! If not, pick yourself up, dust yourself off and try again. It's kind of like the proving ground for a warrior; see if you have what it takes to not fall off the horse.
If you asked me right now what writing contests were available to someone my age and experience, I'd look at you with my mouth gaping open and a dumbfounded expression on my face. I simply don't know of any. And even if I did, I'm not sure that I'd enter one. At best it would force me to sit down and strip what I'm working on to it's bare bones, making it a short story and easily digestible for a contest. At worst I'd write something completely different and loose track of the story that I'm having such trouble with.
Might not be a bad thing, now that I've said that out loud. "Put down the coffee and step away from the laptop..."