I had originally come up with a pretty long-winded workaround for syncing multiple Google Calendars with Windows Phone. I’m happy to say that’s no longer needed as Google finally (and officially) added multiple calendar support for Windows Phone.

1. Using your Windows Phone, browse to http://www.google.com.
   
2. You need to be signed into Google. If you’re not already signed in, you can do it by tapping, well, “Sign In”.
3. Now browse to  http://m.google.com/sync.
4. You should now see a list of your connected devices and one of them should be your Windows Phone. Tap on it.
   
5. You’ll be presented with a list of calendars to sync. Select the ones you want pushed down to your phone and tap Save.
   
6. You are done. Go to your phone and hit “sync” for your Google account. You should now see multiple Google calendars in the Calendar settings.
   
   
   
7. You may have to delete your Google account from your phone and re-add it.

Hope this helped,

Anthony - Wonder Reader for Windows Phone