NameserverChecker.com - Nameserver Checker Tool
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.
CheckNameserver.com - Nameserver Checker Tools
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.
NameserverFinder.com - Nameserver Lookup Tool
NsLookup.io - A simple and powerful tool for querying DNS records