Salesforce Data.com - Data.com provides company profiles and contact information across millions of businesses worldwide.
Hunter - Find all the email addresses related to a domain
FullContact - Put the power of full contact information into your web or mobile apps.
Snov.io - More leads. More sales. More revenue.
HookFeed - Customer Analytics in One Click.
Apollo.io - Apollo’s predictive prospecting, sales engagement, and actionable analytics help the teams to reach its full revenue potential.