Yes there will. It's going to cost $69, cover it for 2 years, and include battery replacement. It will be available sometime during July, but you will be able to purchase it at any time during the first year of owning your iPhone.
Remember, AppleCare is just for manufacturing defects. AppleCare is piece of mind for manufacturing problems that occur in the time period after the one year warantee expires. You won't need to purchase AppleCare before July 28th, 2008.
Search around on the thread, someone posted a link to an Apple reseller that have AppleCare at lower than MSRP prices (AppleCare for iPhone isn't available quite yet though, AFAIK, so no idea if they'll be any cheaper).
Damage caused by you that leads to failure (dropping, bending, drowning) isn't covered by AppleCare. You should also cover it with your homeowners/renters insurance to protect it from your own bad luck! Some people are reporting this is as low as $15/yr through their current policies, and this is something you'll want to get as soon as possible (before you drop it in front of a truck).