These 2 are doable...
www.DomainAffairs.com www.NameRewards.com
But, I think, domain resale sites are a dime a dozen so, try to be innovative or offer something new if you can. You do, have two interesting possibilities for "twists".
For example, DomainAffairs could offer some domain industry info, pehaps something about TM's, protection of the small domain investor against large conglomerate hoarding and stretching TM law, etc.
NameRewards could offer just that, some sort of rewards for registrering and/or selling domains with you (free reg's?)
Good luck, these are worth more developed -- meaning with some concept(s) behind them.