Just added an excellent listing of tools & links from a Klixxx article to our resources:
Over 50 Webmaster Resources - by Dyanna S. Culp
http://www.klixxx.com/archive/over50.html
Under Web Design she's listed:
11. Who Is Search: URL choices are slim-pickings these days. Try these urls to find out who owns a domain name (make an offer), or to see which versions may be available in one of the .com alternatives. Sometimes one site will have owner information missing from the others. (
www.internic.net , estore.netbenefit.com ,
www.enom.com ,
www.tv, www.buydomains.com , International searches at
www.uwhois.com)
Hope this helps!