I know that you can integrate Google calendar with evolution, but it doesn't seems to work for me. Once I add something to my Google calendar, it never updates in Evolution.
Please don't send me to the Ubuntu help wiki page because I already tried following the instructions there a lot of times and nothing works.
Calendar Extension for Thunderbird
Install this plug-in: xul-ext-lightning 
Google calendar and Evolution....
Currently there is a bug in evolution. A workaround to do the following:
How to migrate from evolution to Thunderbird...
I just installed Calender indicator. It's integrated in the top bar of ubuntu and it just shows as a small calender indicator with the date in it. If you click it you can see your google calender which you add on first startup of the program.
I would suggest to try it, it is very small and very handy.
sudo add-apt-repository ppa:atareao/atareao
sudo apt-get update && apt-get install calender-indicator
Next just run it from the Dash. Enjoy!
I'm using Thunderbird with the addon Lightning to integrate my GCal with Ubuntu and I'm happy with that.
