Tunes - Tuneflow

Thunderbird only: Thunderbird extension Google Contacts automatically syncs contacts between your Google and Thunderbird address books. The sync is bi-directional, and the extension is smart enough to detect Gmail accounts you've already set up in Thunderbird, so setup is a breeze. Beyond that, there's not much to it—Google Contacts does exactly what it sets out to do.

Google Sync for BlackBerry updated today, adding support for bi-directional contact sync between your BlackBerry and your Gmail contacts (in addition to the existing calendar sync, which I believe still only supports one-way sync UPDATE: Nope, it's two-way, too!).

Whether you prefer managing your contacts outside Gmail or you don't use Gmail but still want to use Google Contacts to manage your Reader or Docs contacts, try the standalone Google Contacts page. The URL isn't type-in friendly, but it deserves a bookmark if you need to do contact management outside of Gmail.