Hunter - Find all the email addresses related to a domain
AnyMailFinder.com - Find anyone's email address
AeroLeads - AeroLeads is a lead generation software which finds prospects with email and phone number.
Knocker.io - Automate searching for small businesses without a website around the world
LeadGibbon - Access millions of business contacts, with verified email addresses and phone numbers
EmailMatcher - Find anyone's email address in a matter of seconds, for free