Read it
here
I have EAS (Exchange Active Sync, or 'push') enabled. If I go into
Settings
Mail,Contacts,Calendar
Mac (or whatever you've called your .mac email account)
And turn on Contacts or Calendars, it turns on Mobileme push too! I don't get any warnings like I do when I enable Bookmarks.
Now on my iPhone I have the following Calendars:
All Calendars
Exchange (with all my Exchange Calendars listed)
MobileMe (with all my ical Calendars listed)
You can do the exact same thing for your contacts.
Sweet!
Now prior to 'discovering' these setting options. I exported a couple of my ical calendars and imported them into Exchange. They pushed over to my iphone just fine. So those of you using ical and Exchange but not MobileMe, you can still get everything pushed to your iPhone.