Domain Details - Displays Server Type, Headers, IP Address, Location Flag, and links to Whois Reports.
Whoisology - Connected database of whois records and whois history
ViewDNS.info - Free DNS related tools including Reverse IP Lookup, DNS Propagation Checker, Chinese Firewall Test...
WebCargo - Optimize your workflow by offloading it to us. Useful API's with seamless integration that scale to your needs.
Whats My DNS - Instantly check your domain names current IP address and DNS record information against multiple name servers located in different parts of the world.
WhoisThisDomain - Domain name lookup tool that allows you to get information about domain registration from WHOIS server.