The new iPhone OS version 3 just came out with much appreciated CalDAV support. While the main calendar is easy to setup, secondary calendars are a little harder to get to work.
For the main calendar, you put “www.google.com” in the address field and your usual Google login and password and that will add your main calendar.
For a secondary calendar, you need to go on your secondary calendar’s configuration page on the Google Calendar website. On this page you should find a Calendar ID that looks like this :
email@example.com (Note, this is an example)
On the iPhone, in the address field, you need to input the following :
and your normal login and password. This should do the trick!