DiscoverOrg - DiscoverOrg is an IT sales intelligence platform providing technology marketers access to data, IT org charts, and real time projects.
Cardhop - The Mac contacts app you'll want to use.
Clearbit - Clearbit provides Business Intelligence APIs
Google Contacts - Google Contacts is Google's contact management tool that is available in its free email service Gmail, as a standalone service, and as a part of Google's business-oriented suite of web apps Google Apps.
LinkedIn Sales Navigator - Sales tool for LinkedIn users.
Contalist - The contact app for professionals and small businesses