Contact Importer provides a form for your users to enter their email address and password. The contacts from their address book are then retrieved.
Contact Importer can be used with any Drupal form. No codding necessary. It can be used with an invite module, a user import module, an emailing module, or anything else that you can think of.
The current release interfaces with the Octazen or Open Inviter retrieval services. But the architecture is modular and can be very easily extended to use other retrieval services such as Contact Mines, ImproSys, or IpInvite.
Note: Currently the Octazen service is defunct. Some people report issues with Open Inviter. If you would like to create an engine for another service please open an issue and I can give you commit access.