As you found out there are lots of options out there...the only right choice is what's suitable for your needs.
If you are looking at a prime, I think the DA 35 would be a great start. Right in your budget and enough left over for a protection filter.
For the money a used zoom like the other members suggest or pick up a used Sigma 17-70 2.8 -4.5. It's a great lens for the money, you can get up to an inch away from the subject and still have it focus. Out of the lenses I have/had I always seem to fall back on it...the zoom range is just perfect for most of my casual needs and is quite sharp stopped down.
Now if anyone comes out with a 2.8 version I would be the first to jump on it
Good luck with your decision
Thanks
Randy