Does anyone know of a domain registrar that offers API without having buy bulk (become a reseller, etc) domains? Basically, I'm looking to let customers buy & register domains from the registrar, but through my website (as a matter of convenience when they buy hosting). I have no problem with branding or anything. I'll even go with selling as-is, with no profit on my part - I just want to offer it for automatic option when buying hosting from us (instead of registering by themselves, or waiting for us to manually register them).

So far, I haven't found anyone that will let you do that, though.

Do a search by registrar

http://www.internic.net/origin.html