Computing : Domain Names

One and One
One and One offer domain name registration services at decent prices.

Easily
Another popular domain name registrar

123-Reg
Affordable and cheap, but also reliable. Worth a look.

Easyspace
Still a popular provider, and used by many, though their prices are significantly higher than much of the competition.

Nominet
Nominet UK is the registry for .uk internet names. They are the authoritative database of .uk domain name registrations. Also, they are a not-for-profit company and have members instead of shareholders. Worth checking this site out if you are registering a .co.uk domain, and also to update your details should it be necessary, post purchase.