I use [ActiveSync](http://www.google.com/support/mobile/bin/answer.py?answer=138740&topic=14252) to sync with my iPad and iPod Touch to Google for Mail, Contacts and Calendars. You can sync multiple Google calendars to your iPhone and iPad, but configuring it for iPad is currently broken because Google's sync configuration page doesn't recognize the iPad as a mobile browser. There is a solution, however, and that is to use Safari to fool the Google sync configuration page into thinking that you're an iPhone. From your computer (not your iPad), do the following:
1. Open Safari and view Preferences (**Safari->Preferences...**)
2. Go to the Advanced tab and check **Show Develop menu in menu bar**
3. In the menu bar, you'll now see a **Develop** option. Select **Develop->UserAgent->Mobile Safari 3.1.3 — iPhone**
Directions, with screenshots, are [available on Kevin Tofel's page](http://jkontherun.com/2010/04/04/ipad-calendar-sync-fix-google/).