Clearbit - Clearbit provides Business Intelligence APIs
ZaapIT - Mass Merge, auto merge, duplicates cleanup, bulk edit, bulk update, bulk delete , mass lead convert
ZoomInfo - ZoomInfo is a B2B database providing detailed business information on people and companies.
Duplicate Check - Start creating data happiness. Find, merge and prevent duplicate records in your Salesforce Organization.
InsideView - InsideView aggregates and curates all the company and contact data, news and social insights, and professional connections you need to do business better.
Apsona for Salesforce - Apsona for Salesforce is an add-on application for Salesforce to manage the data.