Not too much left to add, but I would look for a nice hardtail mountain bike, or perhaps a hybrid like the trek FX line up. Look for leftovers from 08, otherwise your price range will get you into the bottom two or three FX's.
Hardtail wise, entry level mountain bikes are nearly all the same, the difference is mainly cosmetic and perhaps a very slight change in the frame design. Go to every bike shop in your area and ride everything in your price range, buy from the shop that treats you the best and makes you feel comfortable. Don't forget to budget for a few essentials, you'll need a patch kit, tire levers, frame pump, seat bag to keep them in, and a helmet to keep the ole melon safe(r). All of these should run you right about $100. It stinks having the buy this up front but keep in mind Murphy’s law of flat tires on bicycles: You will only get a flat tire with no means to repair it on the day your wallet and cell phone is accidentally left on the kitchen counter.
Bau