Thunderbird AB Sync Free
The official app & game
Distributed by ApkOnline
Download this app named Thunderbird AB Sync Free.Provides direct transfer of Thunderbird Address Book and Android Contacts data via a TCP/IP network connection (no online uploading of Contacts!).
Android 1.5, 1.6, and 2.0+ supported. See docs for full details (which are also available on the website).
Updates:May 28, 2012: Long overdue update to support Thunderbird 12 (go to the web site to get the updated extension).
Thunderbird AB Sync Free from ApkOnline.net