I recently re-located to TX and have been looking at property. I've found a number of really nice parcels in East TX with ponds on them. I'd say the average price is about $30K for 10-15 acres with a pond, trees and water/power on site. Note this is the part of TX with a lot of oaks and pines and not on the prairie flats. The closer you get to big cities like Dallas however, the higher the price climbs.

You can go to realtor.com and search the MLS list anywhere in the nation. But this only shows properties listed through realtors. Often you can find better deals driving the country roads and looking for signs that say "for sale by owner". That's what I've been doing.