MobileMe is launching in July. The yearly subscription price is $99. If you buy any new Mac you get $30 off from your first year MobileMe subscription.
MobileMe automatically pushes new email, contacts, and calendar events to your Mac or PC and over the air to your iPhone and iPod touch. So no matter where you are, your devices are always up to date. You also get easy photo sharing and 20GB of online storage. There is also a family plan that sells for $149 per year.
More details on Apple Store.