I've bought and sold guitars on Ebay and Harmony Central. Harmony Central has pleasant people to deal with (in my experience) but the site traffic is small compared to Ebay. Ebay is my choice for selling in spite of greater likelihood of encountering flakes and difficult people. Much greater exposure. I've been shocked at how much has been bid for some items on I've sold on Ebay, more than I expected in more than a few cases. You have to know how to write an honest but highly descriptive ad and you need to be able to post high quality photos to maximize your sale.