Finding Domain names registered to someone?

[Kingpin1]

I have a small business and my competitor has a few domain names, some of them I know of and some I dont. I would like to find out what other domain names this person has registered, how can I do this? I have seen a few programs that do this but they cost 75+ dollars. I have seen a site that looks up other domain names in the past but now I cant find it. Thanks for any help

[Blue Gravity]

You can probably just lookup their information through a simple whois, and then take keywords from there, either their email contact info or phone number, and Google it. Sure beats paying for it.

[domainsales]

You may want to try Network Solution's whois. They allow searches by domain name, NIC handle or ip address. No guarantees but may be worth a try.