Does anyone know sources of setting up domain registration on your site?

Try these guys out. www.awregistry.com You have full control over your domains, it will appear as if your are a registrar. Also fully customizable.

That looks like a good one.

I use www.DirectNic.com . $15 a year and they have great tools. It doesn't allow you to appear as a registrar though like the above one.

I use DirectNic for all my domains and love the service...

However for integration with my web hosting company I selected:
http://web.dotster.com/resellers/

Great interface management tools and complete customizable!

I wish DirectNic had something like this!

I wouldn't recommend Dotster. The API is down quite often or slow to respond so customers cannot register or manage domains. Also, if you allow Dotster to handle support requests, it usually takes them two business days to respond and many customers have complained about lack of support. Dotster's API is currently down and has been unavailable for atleast an hour now.

I have decided to register domains through OpenSRS next month.

the obvious.. www.enom.com :)