UProc for Sheets - Boost your sales, marketing and IT tasks from Google Sheets
Senders - Caller ID for your email
Sheetlist - Discover free Google Sheets for marketing, finance and more
LinkedIn Sales Navigator for Gmail - Rich contact profiles inside Gmail
Mattermark in Salesforce AppExchange - Automatically enrich leads in Salesforce with Mattermark
RocketReach - RocketReach allows you to lookup email and phone for 250+ million professionals.