set up calendar for Google calendar and Thunderbird

There are add-ons for the Thunderbird email client that gives a calendar and allows you to synchronise with Google calendar (ie, if you add an event on Thuderbird, it appears on GCal, and if you add an event on GCal it appears on Thunderbird. I haven't yet tried the case of adding an event on Thunderbird while there is no internet connection active, and then later activating it. Hopefully the new event is then added to GCal.
I am using Thunderbird 2.0.0.16
Lightning 0.9
https://addons.mozilla.org/en-US/thunderbird/addon/2313
and Provider 0.5
https://addons.mozilla.org/en-US/thunderbird/addon/4631#reviews

There is a description of how to set these up at
http://bfish.xaedalus.net/?p=239

This seems to be a practical way of synchronising your calendar between a desktop and a laptop.
There are new versions of all these tools coming up (Thunderbird 3.0 later in the year), so some of the details might change, but Mozilla seems committed to adding this as a useful feature.