OpenDNS - OpenDNS provides faster and safer Internet access for your home or Business.
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.
NameserverChecker.com - Nameserver Checker Tool
DNSChecker.org - Check DNS Propagation worldwide. DNS Checker provides name server propagation check instantly. Changed nameservers so do a DNS lookup and check if DNS and nameservers have propagated.
NameserversTool.com - Nameserver Lookup Tool
NsLookup.io - A simple and powerful tool for querying DNS records