I used to use the Mozilla Calander plugin for Thunderbird: Lightning. Haven't used it for long, but today I found that it would be nice to have it back again. I found that it was on my thunderbird plugins but it was not compatible anymore with my version of Thunderbird.

Since Lightning is architecture specific you need the 64 bit version of it. That is: if you use the 64-bit Linux Thunderbird. It is available but for some unknown reason Mozilla did not publish it. Via the Ubuntu site (thanks to the Ubuntu Community) I found the location of the 1.0b2 beta version (for Thunderbird 3.1.x) here. The 1.0b1 version (for Thunderbird 3.0.x) here. Since it is version specific, with new versions you can try it with changing the version id in the url.

Download it, together with the accompanying Google Calendar provider, and install it in Thunderbird.