I don't know that best sites for selling horses on the internet.... hadn't really looked until Ruthy started posting pictures to me of nearby horses.
A friend of mine said she'd had luck selling the horses she raises on Ag Direct. But another friend said he'd had some real nut-cases contact him after posting a couple of horses there. They were trying to scam him out of some money. One wanted to send him a check for more than he wanted for the horse and have him send them the difference. Another wanted to pay him half up front, pick up the horse, then pay the rest later. It was really weird. I guess you have to be real careful on both ends of the transaction. I haven't talked to him in a while so I don't know if he ever had any luck or not.