Now that domain registration has been de-regulated in Canada & the USA, there is large choice of registrars for your Internet domains.
This is not intended to be an exhaustive list, but will indicate the major players. You should compare their price and the after-sales domain self-administration features.
Not all domain registrars are the same!
US/International Domain Registrars
Domain Appraisals/Brokers About Domain Name Appraisals