DNS

• Google DNS
• Multicast DNS
• OpenDNS
• avahi
• dig
• djbdns
• dnsip - look up the IP address of a domain name
• dnsmasq
• dnsmx
• dnsname - look up the reverse DNS of an IP address
• dnstxt
• host
• hosts_file
• nslookup

• DNS Watch - DNS lookups
• SPF Query Tool

Google:

• 8.8.8.8
• 8.8.4.4

Level3:

• 4.4.4.4

OpenNIC:

• 96.90.175.167
• 50.116.23.211
• 50.116.40.226
• 104.238.153.178