AnyMailFinder.com - Find anyone's email address
Hunter - Find all the email addresses related to a domain
Norbert - Norbert is an online tool that helps you to find anyone’s corporate email address.
GitHub Email Finder - Find the email of any GitHub Developer using their GitHub username.
LeadGibbon - Access millions of business contacts, with verified email addresses and phone numbers
Paxtac - A free extension to find email with a full name and domain.