I typically find places like AR's CL will have the best deals, but the worst availability. So you're likely to get a LOT of bike for a little money, but could take a LONG time 'til you find the right bike.
Google maps makes it look like you're in the middle of MTB heaven!
This is a good one if it's your size, and in good shape. It probably doesn't have front shocks, if you'd like them, however.
Giant Rincon for $150 this may be more like it if you like front shocks. Size 17".
Trek for $200, not many details, but could be good.
Where would you rather drive? Fayetteville or Little Rock? If either one's OK, try using crazedlist.org to search both at the same time.