PCNames Domain Search is a great tool to check everything about a domain name. Based on Ajax, you just have to type a name and results appears fastly. I have tested it and I’m convinced, although .eu and .uk are missing in search results. You can see instantly disponibility of domain name and its « Whois ».
Besides, I have appreciated the « Suggest Service » too. Interface is the same but you type a word and engine suggests different domain name (around this word),which are available. I read about it in a lot of detail in the SearchEngineWatch blog.