Gmail now adds people you email with to your contact list after several correspondences, rather than after you email someone for the first time. Contacts you add manually or through an import are also saved in 'My Contacts'. People you haven't had many email exchanges with are auto-added to 'Suggested Contacts', and you can move those people to 'My Contacts' at any time.

Editions impacted:
Standard, Premier, Education and Partner Editions

Languages impacted:
US English

How to access what's new:
Sign in to Gmail and click 'Contacts' to browse 'My Contacts' and 'Suggested Contacts'.

For more information:
http://www.google.com/a/help/intl/en/users/gmail.html