Search in the google for the "webmasters forums" and see if it is listed sites have a "buy, sell and trade" section for domain and webpages. If they do, create an account and put a message describing what you're selling. Potential customers will contact you for details.
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I have sold domains via different venues, incl. right here on WebHostingTalk, another hosting related forum, DNForum, former GreatDomains, former Afternic, Sedo and even a non-domain/hosting forum.
So far (over the last 10 years), DNForum has worked best for me, partly because almost most big players are members there. Sales may not come directly from a post or thread but PM (Private Message) BECAUSE of your exposure there. Sedo is not bad either, and they have a good European (and lately Asian) clientele that many US-based websites/forums don't have much access to.
Co-Founder@HostHideout. Profoundly influenced by #Bauhaus, @Nameslave unrepentantly embraces #Minimalism with a bias for functionality, color theory and pixel precision: a #multimedia messenger in the McLuhan sense. His totally irrelevant M.Ed. dissertation examines Organizational Culture and Change Management. He also likes Patrik Ervell, Wong Kar-wai and IKEA.