I used to have a MobileMe account because I wanted all my contacts, files and calendars all in sync on my various iDevices. After a while Google and DropBox made it possible to do everything MobileMe could do without having to spend the $99 a year. So I canceled my MobileMe account and moved to using Google and DropBox.
The one thing that I couldn’t figure out was how to add multiple Google calendars to my iPhone. Then I found it. The link that changed all that. Ok its not that much of a break through but just go to http://www.google.com/calendar/iphoneselect and choose the calendars you want to show up on your iPhone.