How do you synchronize Google Calendar and iCal?

"I use BusySync - largely because I needed this functionality before there was any other way to do it.

It works really well for me. The three or four calendars I subscribe to from Google calendars are Read-Write, and the fields match up pretty well.

I have looked at other options, but never pursued them, as the current method for me works fine."

"Very much interested in the question myself. You probably know that you any Google Calendar comes with its ICal file that you can reference from third-party apps. But the feed leaks more information than as per the original calendar's privacy settings. And Google's VFREEBUSY feed just doesn't do what it's meant to do.

For a business app where I originally thought of using third-party software to synch up an events database with Google Calendar I had to roll my own and parse the ICal feed directly."
"Very much interested in the question myself. You probably know that you any Google Calendar comes with its ICal file that you can reference from third-party apps. But the feed leaks more information than as per the original calendar's privacy settings. And Google's VFREEBUSY feed just doesn't do what it's meant to do.

For a business app where I originally thought of using third-party software to synch up an events database with Google Calendar I had to roll my own and parse the ICal feed directly."

There's also Calaboration. Very easy to use.

"I am not sure if BusyCal is the same BusySync (if it is I apologise)

Update: I have been informed that BusyCal replaced BusySync. Therefore scroll down to my second answer.

Download the 30 day trial of BusyCal 2, and if you think its to your liking you can always purchase it afterwards.

Example Screenshots:

It is described as:

An award winning calendar that provides powerful time-saving productivity tools in a friendly, personalized, easy-to-use package.

BusyCal's unique and powerful features include customizable calendar views, scrolling Month and Week views, an integrated Info Panel for quickly viewing and editing events, integrated To Dos that display in the calendar and carry-forward until completed, custom font sizes and styles, graphics, live weather feeds and moon phases, and a menu bar app for quick access to the current day's events and weather.

BusyCal takes full advantage of the latest features in Mountain Lion, including the Notification Center for displaying alerts and banners; and Application Sandboxing for safe computing. BusyCal is compatible with iCloud, Google Calendar, and other CalDAV servers, enabling you to sync and share your calendars through the cloud with other Macs running BusyCal or the built-in Calendar app on OS X, as well as iPhones and iPads running the built-in Calendar on iOS 6.

Available: http://www.busymac.com/busycal/

Alternatively:

An application called Blotter

Available from: http://wireload.net/products/blotter/

The link below tells you about using Blotter with Google Calendar depending on which version of Mac OS you are running:

http://support.wireload.net/entries/455852-can-i-use-blotter-with-my-google-calendar"