iCloud

UPDATE: MobileMe has been superseded by iCloud.

Sometimes MobileMe will have problems syncing your data across multiple devices. Ideally, the service will keep ten items (Bookmarks, Calendars, Contacts, Dashboard Widgets, Dock Items, Keychains, Mail Accounts, Mail Rules, Signatures/Smart Mailboxes, Notes/Preferences) synced between your computers, iPhone and other devices. When and if this process stops working properly you can try the following steps to reset your sync.

UPDATE: MobileMe has been superseded by iCloud.

You must be a MobileMe subscriber to use MobileMe features on the iPhone. Once you've purchased a year of MobileMe service from Apple, here's how to set it up on your iPhone:

1. Touch Settings -> Mail, Contacts, Calendars
2. Select Fetch New Data -> Push ON
3. Navigate back to the Mail, Contacts, Calendars settings and choose Add Account
4. Choose MobileMe
5. Enter your account information and touch Save
6. Mail -> ON
7. Contacts -> ON
8. Calendar -> ON
9. Bookmarks -> ON
10. Find My iPhone -> ON