Only the default calendar is sync-ed when you setup your google account on your device for the first time.

If you have used a [Gmail] account to synchronise your device,
visit the following URL to enable additional calendars, https://www.google.com/calendar/iphoneselect


If you have used a [Microsoft Exchange] account instead, visit the following URL on your phone, http://m.google.com/sync

Depending on what you would like to synchronise to your device, you have basically 2 options to choose from.

Choose [Gmail] if you would like to synchronise google notes to your device

Choose [Microsoft Exchange] if you would like to synchronise google contacts to your device. [Exchange] account also allows you to sync a public shared calendar to your device.

The following steps are for setting up a google exchange account

1. Go to [Settings]
2. Select [Mail, Contacts, Calendars]
3. Choose [Add Account...]
4. Select [Microsoft Exchange]
5. Enter your full email address in [Email] and [Username]
6. Enter your password in [Password]
7. Click [Next]
8. The verification take place, and the [Server] field will appear
9. Enter 'm.google.com' in the [Server], without the quotes
10. Click [Next]
11. You could choose to sync Mail, Contacts or Calendars now.
12. Finally, click [Save]!

1. Go to [Settings]
2. Select [Mail, Contacts, Calendars]
3. Choose [Add Account...]
4. Select [Microsoft Exchange]
5. Enter your full email address in [Email] and [Username]
6. Enter your password in [Password]
7. Click [Next]
8. The verification take place, and the [Server] field will appear
9. Enter 'm.hotmail.com' in the [Server], without the quotes
10. Click [Next]
11. You could choose to sync Mail, Contacts or Calendars now.
12. Finally, click [Save]!

http://email.about.com/od/iphonemailtips/qt/How-To-Add-Free-Push-Windows-Live-Hotmail-To-Iphone-Mail.htm