Thunderbird

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/

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/

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

Spread Thunderbird
The official community marketing site for Thunderbird. Buttons and banners, affiliate program and forums.
http://www.spreadthunderbird.com/

Thunderbird Add-ons
Add-ons are extensions and other additions that add new functionality to Thunderbird or change its appearance.
https://addons.mozilla.org/thunderbird/

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

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/

Mozilla.org: Thunderbird 1.0 Email Client Has Landed
Official press release covering the launch of version 1.0. <small>(December 7, 2004)</small>
http://www.mozilla.org/press/mozilla-2004-12-7.html

The Rumbling Edge
Weekly developments in Mozilla Thunderbird builds. [RSS]
http://weblogs.mozillazine.org/rumblingedge/index.rdf