How can I show multiple Google calendars in iPhone's calendar app?

There is an easy but non-obvious way to do this.

Assuming you've got Google sync set up, and you can see your one Google Calendar on your phone already, go to https://www.google.com/calendar/syncselect (it needs the www; it doesn't have to be on your iPhone). You'll see a list of devices you're syncing. Select your iPhone.

On the next screen, you can choose which of your Google Calendars you want to sync with your iPhone. Check the box next to the desired calendars, then hit Done or Save or whatever it says at the bottom.

Open iCal on your iPhone, and give it a while to sync, and you now should see all of your selected Google Calendars on your iPhone.

For some reason, you can't change the colors of the calendars on the iPhone, so I change the colors in Google Calendar to match what the iPhone picks.

There used to be a limit of 5 Google Calendars that you could sync to the phone, but they recently raised the limit to 25.

These same instructions apply to the iPad and iPod touch. I've got this set up on all my devices, and it works like a charm.

This is documented by Google here: http://www.google.com/support/mobile/bin/answer.py?answer=139206

I believe you can only do one Google calendar per account to the iPhone. You can sync multiple Google accounts.

Here are some instructions, but I was unable to get it to work: http://www.google.com/support/mobile/bin/answer.py?answer=139206

It would be a nice feature to have.

You'll need to create a different account on the iPhone for each calendar, but they can all point to your one Google account...

1. You probably already know which calendar is the "main" one, as that's the one that the iPhone reads when you add the Google account. You may have to delete that one from the phone (not from Google, of course) for now because sometimes the phone will complain that "you already have an account for this set up."
2. For each non-main calendar, go to the calendar details on the Google Calendar web site and look for the "ICAL" icon under the "Calendar Address" section.
3. Add the account on your phone, then edit the details for that account and enter the address from #2 above as the URL for the calendar. (Under Advanced Settings)
4. Rename the account on the phone accordingly so you know which calendar it is.
5. Repeat for each non-main calendar.
6. Finally, add the account as normal for the main calendar.

It's a bit of a hack, and I really wish there was better native support for multiple calendars in all kinds of applications/devices that interface with Google Calendar. But, for now, this has been working really well for me. It's just a pain to set it up in the first place.