Domainer - Manage All Your Domains and Websites
WhoisThisDomain - Domain name lookup tool that allows you to get information about domain registration from WHOIS server.
Domain-Monitor.io - Looking for the complete domain and website uptime monitoring solution? Domain Monitor keeps an eye on your website, cron, SSL and domain name 24/7 and will alert you through Email, SMS and web when something stops working.
WebCargo - Optimize your workflow by offloading it to us. Useful API's with seamless integration that scale to your needs.
HTTrack - HTTrack is a free (GPL, libre/free software) and easy-to-use offline browser utility.
Bulk Whois API - Bulk Whois API is a provider of parsed WHOIS data in JSON with simple API, competitive pricing, top notch support, and more.