It's very easy (and cheap) to register a domain name. Sites like GoDaddy and Register.com are cheap, fast, and reliable. However, you can only register your domain with '.com', '.net', '.org' and a few other common root domains. If you are looking to register a .ca domain name for an organization or business that is Canada-specific, then here's a great site to use.
Formerly RegisterSite.com, the company is now called Misk. You can register your Canadian domain with them. You can even register a site at the provincial domain level, such as '.on.ca'.
I am not in any way affiliated with Misk, and I don't get anything by you signing up with them. I have just found them to be very reliable and professional, and I thought I'd share the info. By the way, I use them now for all my domain registrations, not just Canadian!