I've been informed of 123 Domain Names which is a resource that can be used to register domain names. It's very straightforward to use - just type in what you want to register and see what it comes up with. The most impressive thing however is the sheer number of alternative options you're given. All of the obvious choices, such as .com, .co.uk, but also ones such as .plc.uk, European domains such as .gr, .no, .pl and some international options.
If you're looking to register a domain, then this is a good resource to take a look at. Thanks Adrian!