Tucows.com is still working on the site, but their
Open Shared Registration System
should be ready to go by November15. There's an API to proxy through their accredited server into the domain name database. Anyone can write their own client software based on theirs, which is GPLed. Their take is $13/year, easily the lowest yet: the idea is for others to customize their own client software, add value, resell domains, and start the price war.