DomainTools - Domain name research, including comprehensive Whois Lookup, Reverse Whois Lookup and Whois History.
ViewDNS.info - Free DNS related tools including Reverse IP Lookup, DNS Propagation Checker, Chinese Firewall Test...
Online Domain Tools - Online-Domain-Tools.com makes your online life easier and happier.
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.
NsLookup.io - A simple and powerful tool for querying DNS records
DNSdumpster.com - Open source domain intelligence lookups for security recon