BirdieSync
   Pocket PC and Smartphone synchronization of cards, events, tasks and mails with Thunderbird, Lightning and Sunbird on ActiveSync and Windows Mobile Device Center.
   http://www.birdiesync.com

Lightning
   Project to provide the functionality of the Sunbird calendar application as a thunderbird extension. Includes download and FAQs.
   http://www.mozilla.org/projects/calendar/lightning/

Mozilla.org: Thunderbird 1.0 Email Client Has Landed
   Official press release covering the launch of version 1.0.
   http://www.mozilla.org/press/mozilla-2004-12-7.html

MozillaZine Forums - Thunderbird
   Messages about bugs, features, builds, and the program in general.
   http://forums.mozillazine.org/index.php?c=8

Open Source Articles
   Detailed installation guides and tutorials for Thunderbird
   http://opensourcearticles.com/thunderbird_15/english/part_01

The Mozilla Thunderbird Mail Project
   Goal is to produce a cross platform stand alone mail application using the XUL user interface language.
   http://www.mozilla.org/projects/thunderbird/

The Rumbling Edge
   Weblog about developments in the nightly builds.
   http://weblogs.mozillazine.org/rumblingedge/

Thunderbird Extensions
   Extensions are small add-ons that add new functionality to Thunderbird.
   https://addons.mozilla.org/thunderbird/extensions/

Thunderbird Portable
   Full featured version for portable devices such as USB drives
   http://portableapps.com/apps/internet/thunderbird_portable

Thunderbird Themes
   Themes are skins that allow you to change the look and feel of the browser and personalize it.
   https://addons.mozilla.org/thunderbird/themes/

Thunderbird on Wikipedia
   In depth history and information
   http://en.wikipedia.org/wiki/Mozilla_Thunderbird