A new secondary domain name market option is now available at the registrar level. The Global Domain Name Exchange (GDNX) is an exchange created for and supporting the valuation and transfer of previously registered or held domain names. Its membership is open to ICANN-accredited registrars and registries. Information about GDNX can be found at GDNX.org.
This looks promising, but note that this is not a new front end service for the typical domain name owner. Instead, it’s a backend service for registrars that will allow them to offer the services to you as a domain name owner. *IF* the network takes off, this could be extremely valuable. For example, if someone searches for a domain that you have already registered, it could allow them to buy the domain from you. Some registries, like Register.com, already offer a service like this (in Register’s case it’s an agreement with Afternic.com).