SyncKolab 2 syncs your Contacts and Calender in Thunderbird (kolabsys.com)

SyncKolab is now available via the Mozilla Add-On Directory. Combined with the Lightning calendar add-on SyncKolab turns Mozilla Thunderbird into a capable Groupware client. It is released as Free Software under the Mozilla Public License version 1.1 and based on Open Standards for full interoperability. it possible for professional users to collaborate and share data between users of Thunderbird, KDE Kontact, Roundcube, Microsoft Outlook, or mobile clients connected through ActiveSync.