GRC Port Scan - GRC Internet Security Port Scanner. Tests for open ports on your external IP address.

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.

My Public IP - My Public IP is a utility to let you know through which internet IP the world see you.

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.

whatismyip.cc - External IP Address lookup tool with option to scan the external IP address.

NsLookup.io - A simple and powerful tool for querying DNS records