The messages at http://forums.wcha.org/showthread.php?57 are the best information about the worth of a canoe like yours. The classifieds at http://classifieds.wcha.org/ are often one of the fastest ways to find a good new home for a canoe like this if you plan to sell it.
You have the Old Town canoe with serial number 215576 which shipped in July of 1978 according to the information at http://www.boatsafe.com/nauticalknowhow/hin.htm which can help you decode your hull identification number. The scanned Old Town records stop at 210999 so none of us here have any newer information for canoes like yours. Good luck and feel free to reply here if this doesn't answer your question,