A friend of mine recently introduced me to a site called Instant Domain Search. It's a little AJAX app that looks up domain name registration information very quickly. I used to use the command line to do this:
% whois hackaddict.net
This method was a lot faster than going to any website to lookup registration info, but Instant Domain Search is even faster than the command line lookup.
Below is a widget they have on their website. Give it a try.