As the previous post mentions, the visitors center at www.visitcolumbusga.com is a great resource.
Having worked in downtown Columbus for several years - though I am now in Atlanta - I recommend the Cannon Brew Pub, Country's BBQ (both downtown) or Dinglewood Pharmacy (http://local.yahoo.com/details?id=13901929), an old fashioned drugstore that serves a nice slawdog just a mile or so down the road from downtown.