I often need to do a whois search quickly while on the phone with someone and grew tired of Captcha codes and the hassle of trying to find the whois lookup at most registrar's sites. The fastest , captcha free, and most convenient tool i've seen for this is at the following domain. http://www.whois.sc/ The domain in visual is simple enough, however its function comes in its ability to search from the URL bar, for example if you go to http://www.whois.sc/digitalpoint.com It will take you directly to the whois record for that domain. This whois-engine will cover the gamut of most TLD's and popular domain extensions. After a certain amount of searches, you will be prompted to create a login, but even this comes at no cost, and does not need to be added every time you connect. Good stuff
if you're trying to register a domain and find it is available then don't whois it multiple times on whois.sc I found that they must have somehow are in an agreement with some company so let's say if a particular domain that have been whois-ed for more than 10 times isn't registered they get it because it's in demand I guess... Although I offer no proof for this it is just hypothesis.