Google+ integrates with Gmail and Contacts

Gmail and Contacts have got better with the integration of Google+. You can now grow your circles, filter emails and contacts by circles, keep all your contact information up-to-date automatically and share photos to Google+, all right from Gmail and Contacts.

Ability to add contacts to your Circles from your email

Ability to filter emails by Circles you care most about

Automatically updates contact information (not too good IMO)

Share attachments effortlessly without leaving your inbox

» Gmail and Contacts get better with Google+ | Official Google Blog