AdiInviter Pro - The ultimate contacts importer and tell-a-friend system for your website.
Landing Pages in MailChimp - Easy to build, custom landing pages for free
CloudSponge - Companies from every industry use CloudSponge’s Contact Picker to get access to their users’ address books.
Viral Loops for Startups - Virality for startups made easy 💪
OpenInviter - OpenInviter is a free import contacts (addressbook) script from email providers like Mail2World...
Carrd - Simple, responsive one-page site creator.