Today is the last day you can purchase AppleCare+ for your iPhone 4S or iPhone 4, if you purchased it on October 14th or after. AppleCare+ was announced along with the iPhone 4S, and is available for $99 (two years). The plan not only gives you phone and genius bar support coverage, but also accidental damage coverage with a $49 service charge. The plan covers up to two accidents. $99 is a pretty solid insurance policy (Square Trade offers the same).
However, for new iPhone 4S purchases, the AppleCare+ protection plan can be purchased with the device on that day. Today was just the end of the grace period Apple instated for pre-orders. Thanks for the reminder Marco!