I am aware of Sedo, Godaddy Autions and Afternic. I don't like their added fees and commission rates. Sedo wants Appraisals for domain names selling for more than $10,000. I am not sure why.
Other than putting a For Sale sign on the web site, what are free or inexpensive resources to advertise that a domain name is for sale. Looking for something like For Sale by owner directories for domain names.