AdiInviter Pro - The ultimate contacts importer and tell-a-friend system for your website.
AffiliateWP - A powerful affiliate marketing solution for WordPress.
CloudSponge - Companies from every industry use CloudSponge’s Contact Picker to get access to their users’ address books.
ReferralMagic - Turn your users and customers into referral magnets.
OpenInviter - OpenInviter is a free import contacts (addressbook) script from email providers like Mail2World...
Echo - Golang HTTP server framework