Check out the new Active Whois plugin for firefox. It lets you get all Kinds of Whois Info - DNS record, Domain Owner and IP Address.
So whats different from the other whois tools existing for ages (I mean 3-4 years).
One , it is integrated within your browser
Two, it also installs a whois application on your system. So you can simpley check it by opening the application (without the browser)
Three, It keeps the record of the whois that you have already checked. I'm not sure how big the storage is, but I'm guessing enough to check all whois in a session.
Visit the link to download it Active Whois Plugin