Syncman synchronizes your Mac's built-in Address Book with your Gmail Contacts with a minimum of fuss, hassle and frustration.
Three different synchronization strategies:
Bi-directional sync between Address Book and Gmail
One-way synchronization from Address Book to Gmail
One-way synchronization from Gmail to Address Book
Support for most standard contact fields:
Name, Company, Title & Notes
Email Addresses & Phone Numbers
IM Accounts (AIM, Jabber, MSN, ICQ & Yahoo)
Scheduled synchronization with configurable ‘bother level’
Can optionally run in the menubar as a background application (especially handy when using scheduled synchronization)
Shows you all proposed changes before it makes them
Optionally synchronize Gmail's “Suggested Contacts”
Works with both Gmail and Google Apps