Clearbit - Clearbit provides Business Intelligence APIs
6sense - 6sense is a B2B predictive intelligence engine for marketing and sales.
ZoomInfo - ZoomInfo is a B2B database providing detailed business information on people and companies.
Leadiro - Seriously Smart & Live B2B Data
InsideView - InsideView aggregates and curates all the company and contact data, news and social insights, and professional connections you need to do business better.
LinkedIn Sales Navigator - Sales tool for LinkedIn users.