Thanks to Peter Weibacher's efforts, a port of the Mozilla Thunderbird calendaring extension "Lightning" version 0.3 is now available.
On at least *some* installations of both the official, and Peter's unofficial version of Thunderbird, after installing Lightning, Thunderbird will not re-open. If this should happen to your installation, you can easily uninstall Lightning cleanly by right clicking on the Thunderbird object, selecting Properties, and entering -safe-mode in the Parameters box. When you restart Thunderbird, go to the menu bar, and click on Tools -> Extensions. Right click on the Lightning extension, and select Uninstall. Shut Thunderbird down, remove -safe-mode from the Parameters box, and you can now start Thunderbird as expected.
Good luck,
Sander Nyman
Source: OS2VOICE