SugarCRM is a customer relationship management (CRM) system.

FullContact gives you all the power of your address book, right in your Gmail inbox.

Soocial provides a synchronization service that syncs contacts between the users' computers, phones and web apps.

Kolab Now is a web-based email and groupware service, based completely on free and open-source software.

Memotoo sync all your contacts from Gmail, Facebook, phone, Thunderbird, Outlook, etc in a single address book.

AdiInviter Pro is a contact importer and tell-a-friend platform.