Have you added a Google calendar and it’s not showing up on your Android device?

Try this:

Go to Settings > Applications > Manage Applications > All

Then:

Calendar > Clear data

Calendar Storage > Clear data

Google Calendar Sync > Clear data

Then go into Accounts & sync and perform a Sync now

Your new calendar should now be visible on the device.

If you’re also syncing an iPhone, go to http://m.google.com/sync from your iPhone and select which calendars will be visible on the device.