DomainTools - Domain name research, including comprehensive Whois Lookup, Reverse Whois Lookup and Whois History.
WebCargo - Optimize your workflow by offloading it to us. Useful API's with seamless integration that scale to your needs.
CubDomain - CubDomain.com is the site to check website's statistics, Information, Whois Record, Hosting...
WhoisThisDomain - Domain name lookup tool that allows you to get information about domain registration from WHOIS server.
Online Domain Tools - Online-Domain-Tools.com makes your online life easier and happier.
Whoisology - Connected database of whois records and whois history