ContactOut - ContactOut is a chrome extension to find emails and contact numbers.
Hunter - Find all the email addresses related to a domain
Find Email Address - Highly Accurate Email Finder and Verifier
Snov.io - With Snovio you can find emails, verify them and run your email campaigns within minutes.
RocketReach - RocketReach allows you to lookup email and phone for 250+ million professionals.
Mail Dump - Powerful Extensions for email addresses extracting, verifying and finding