UProc for Sheets - Boost your sales, marketing and IT tasks from Google Sheets
Clearbit - Clearbit provides Business Intelligence APIs
Email Verification on Google Sheets - An add-on for email verification directly in Google Sheets
ZoomInfo - ZoomInfo is a B2B database providing detailed business information on people and companies.
Sheetlist - Discover free Google Sheets for marketing, finance and more
DiscoverOrg - DiscoverOrg is an IT sales intelligence platform providing technology marketers access to data, IT org charts, and real time projects.