Few days ago I released the first version of OmniContacts.
As it says in the README:
Inspired by the popular OmniAuth, OmniContacts is a library that enables users of an application to import contacts from their email accounts. The current version allows to import contacts from the three most popular web email providers: Gmail, Yahoo and Hotmail. OmniContacts is a Rack middleware, therefore you can use it with Rails, Sinatra and with any other Rack-based framework.