I've recently configured 3 iPhones - one for Emily, two for friends. So the configuration routine is fresh in my mind and ready to share.
I'll hopefully update this with some reference links, but here's the quick summary. The phones are configured around Google Services, except for Contacts which are a festering sore in Google-Land.
- Check version (lately has been 3.1)
- Turn off auto-ask WiFi
- Picture of business card as wallpaper (so phone can be returned if found)
- Google-phone configuration
- Auto-lock to 2 minutes, show passcode lock
- Mail: Show To/CC label, Signature, Default account (if needed),
- Contacts: Sort and display order, Default account (if needed)
- Calendars: Time Zone support Off, Default Calendar (if needed)
- Demonstrate use of the Search screen
Google-phone configuration (calendar sharing)
- Mail: Default iPhone Gmail setup (IMAP)
- Google Calendar Configuration including Calendar subscription and sharing
- Calendar and Google Contacts: Exchange Server ActiveSync then Google Sync so phone can display multiple Google Calendars selected from the primary Google Calendar collection (m.google.com and tap on "Sync") . Warning: This setup tries HARD to get you to wipe out all other iPhone accounts. Be careful not to do so. In the setups I do people sometimes need to sync with an Outlook desktop calendar, and they almost always need to sync to a desktop Contacts collection. 
- Desktop Contact synchronization (this is controlled by iTunes) 
Third party apps (install and configure)
- Google Mobile (m.google.com)
- Optional: Appigo Tasks.app sync to Toodledo
- No Google task sync solution
- Google Contacts smell of squashed skunk
- Only one Exchange Server account per phone (CalDAV?)
See also: My iPhone Home Screen
 For Google Apps setup see a recent Google Sync post of mine.
 The one substantial advantage of MobileMe for Mac users is the Contacts integration. If the Calendar sharing were not so pathetic and the data lock not stronger than Sauron's Ring it would be interesting.