First off, I really recommend you take a good standing conformation picture of him and put him on DreamHorse. It is only $20 for a picture, the ad is included. Price him at $1200 if he is registered, and $1000 if he isn't. And if you know his bloodlines make sure you fill that out. Also Horse Clicks lets you put up to 4 photos in with an ad for no charge. Horseville lets you do a text ad, and there are some others that do one picture with text for an ad at no charge. These horses are the in thing right now since many riders are into the age bracket where bouncing on the trail isn't that much fun.
Good luck with your sale. If he was closer to me he would be in my barn.