You already know that your smartphone can replace your wayward billboard. It can also help you do away with your keys and security cards.
You don't really need a key to get into your car. Nor do you need that jagged bit of metal and plastic for engine ignition. All you really need is permission. And your NFC smartphone might soon be able to give you that permission. Just wave your phone to unlock your car; then tap the dash to fire up the engine.
When you arrive at work, you don't need to show your ID badge to a security guard. You don't even need your badge anymore, because your phone tells the NFC access point exactly who you are and unlocks the door for you.
Then, when arrive at home from a long day at the office you won't need to dig through your purse for your keys. Your phone will unlock your apartment or house door so that you can waltz in without even the need to twist a key.
So although many of the first uses of NFC will likely apply to intangible digital payments, these examples show how NFC can grant access to all sorts of real physical places. You'll have few items to carry with you, too -- just don't lose your smartphone in the couch cushions.