AnyMailFinder.com - Find anyone's email address
NeverBounce - Real-time email verification and cleaning to ensure emails never bounce.
Hunter - Find all the email addresses related to a domain
Email List Verify - The Fastest Way to Improve Email List Deliverability and ROI
AeroLeads - AeroLeads is a lead generation software which finds prospects with email and phone number.
ZeroBounce - Removes invalid emails from your list to prevent email bounces from ruining your deliverability.