The organisation in charge of accrediting registrars is called ICANN (Internet Corporation for Assigned Names and Numbers)
Here is a list all accredited registrars, if you search the web for a registrar, you will come upon companies that are not listed here, it doesn’t mean they are fraudulous and shouldn’t be trusted. Many registrars have reseller programs where they sell bulk domain registrations and their resellers set up business selling domains and looking legit. These resellers can in turn have resellers who set up business, you get the point. However, when choosing a registrar, my advice is to try and cut as many middlemen as possible. And it’s not even a question of costs, since it might not be more expensive to buy from an accredited registrar than from a 3rd level reseller. The problem is if one of these middlemen goes out of business. It has happened to me and while I was able to recover my domain from the accredited registrar (by sending all kinds of info about the company proving the domain is really mine,) I had to pay my fees twice that year because the first guy went out of business with my money and without paying his provider. It was also a lot of stress and hassle. While accredited registrars can go out of business as well, the fewer links between your and the ICANN, the less chances of a weak link.
Also, don’t let yourself be fooled by e-mails or snail mails from official sounding companies that are NOT your registrar telling you that you are about to lose your domain. I have received such letters and the name of the company suggested a government link when it was really just spam to try and get me to change registrar. This is barely ethical and I recommend against using such companies.
How was the registrar able to find my mailing address? Because when you register your name and address are added to the registry and other users can “whois” you and find your info. Just put “whois domain” in a search engine and you will have dozens if not hundreds of whois tools (here is the one for Google.ca for example.) There are anonymous registry services as well that let you register a domain and the registrar pus own info in the registry. The problem then is, how will you recover your domain if the registrar goes belly up? Effectively the domain is registered to them, not to you! I’d rather have a little less privacy and knowing that I own what I bought.
Another point to be aware of, is that some registrars have hidden fees, that is, they advertise a price but once you have registered your domain with them, they want more money for basic stuff such as pointing your domain somewhere. They often have a hosting service they are try to push but you should be aware of such fees before signing in. Other registrars also put up a fight if you decide to switch to another registrar so it’s worth checking a registrar’s reputation.
For all it’s worth, I currently use 1&1 Internet amongst others and have used ExpertSRS and EZhosting in the past and have been satisfied as well.