How can I sync multiple Google calendars in iCal?
Create a new google account for each calendar. 

Or ask your favorite search engine and find the answer quite at the top of the list. For example, this one http://www.ehow.com/how_8251009_sync-multiple-google-calendars-ical.html.

Added 2012-09-07:

It seems to be even much easier. Under Settings->Account enter the credentials to access the primary calendar on google. Then select the pane "Delegation". There you will find your other calendars, select "Show" and violà, they will appear in iCal (at least under Mountain Lion).