DiscoverOrg - DiscoverOrg is an IT sales intelligence platform providing technology marketers access to data, IT org charts, and real time projects.
Whoisology - Connected database of whois records and whois history
Clearbit - Clearbit provides Business Intelligence APIs
WhoisThisDomain - Domain name lookup tool that allows you to get information about domain registration from WHOIS server.
Datanyze - The sales prospecting tool powered by technology data
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.