Tough one. Columbus Iron Works was in business from 1853 to the 1970s. According to this site they made stoves from 1902 on:
http://www.conventiontradecenter.com/history.cfmHow big is yours? Here's a rather small one that was estimated at $50-100 but only sold for $15. http://www.liveauctioneers.com/item/1875815 Sometimes that happens though so don't be discouraged. It can be difficult to sell large heavy furniture-type items online, you may want to consider Craigslist or your local classifieds.
A similar small one someone's selling for $150: http://www.homesteadingtoday.com/showthread.php?t=390649
It looks like there was another question about a Columbus Iron Works pot-bellied stove on this forum and someone estimated it at $500: http://www.antique-shop.com/forums/index.php?topic=2823.0;wap2
I found multiple people looking for values on Columbus Iron Works stoves but not a whole lot of answers. I'm not one for selling big household items like this and don't know much about yours but I did try to look online for you.