For that price, you won't find any decent full sus. Go for a hardtail, you could get a pretty nice setup at the upper end of that price range.
Hoodslayer's got it. The hardrock is just about the best deal for your money, and it'll last forever. I've seen one take gnarlier crashes than anyone should ever have to witness. While parts come and go, the frame should last you for a long, long, long time.
However, the tires that come stock on the rockhopper are perfectly fine, and I wouldn't get new ones until those die.
When that happens, I'd reccomend slightly more mountain-oriented tires than he did. Go for kenda small block 8's
http://www.jensonusa.com/store/product/TI407A04-Kenda+Tomac+Small+Block+8+Tire.aspx?sc=FRGL
although they'll cost you about $35 each, they are well worth it.
By the way, that website is legit, so feel free to buy from there. I
haven't personally, but I know many people who have had happy endings
in buying bike stuff from there.
Peace out.