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.
Whoisology - Connected database of whois records and whois history
DNS Propagation Check - DNS Propagation Check is an online tool that allows you to instantly perform a DNS lookup against any domain names or IP addresses.
WhoisThisDomain - Domain name lookup tool that allows you to get information about domain registration from WHOIS server.
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.
JSON WHOIS API - Parsed domain WHOIS data from any WHOIS server via RESTful API with metered pay as you pricing.