Sync Your iPhone With Google Calendar
Then, find the Private Address section and click on the ICAL icon. This will generate a URL for your calendar.
Open up iCal and go to Calendar -> Subscribe. Paste the URL from the Google calendar here.
Once your iCal is subscribed, your next iPhone sync will dump all your Google calendar events right in.
Done! The best part is you only need to do this once -- iCal will grab new appointments at your specified intervals and your next sync will be up to date.