What are ideal gifts for teenage girls?

As a teenage girl myself, I can say that of the various options out there, you can never go wrong with anything music related. Depending on the teen herself, I would recommend CDs, iTunes giftcards, or an iPod/Mp3 player. The latest and best (and one of the most expensive) iPods is the iPod Touch, which is extremely admired. Also, you may try adding to a collection your special teen may have started. See if she shows an interest in Vera Bradley bags, another purse collection, or a certain book series. If the girl you're shopping for has a car or frequently drives one, a giftcard to a gas station would be nice and appreciated. Even if you can only purchase a card for one tank of gas, you have still made a difference. Facials, manicures, pedicures, and hair stylings are always welcomed. Find out if the girl you're shopping for has visited a salon or spa and get a giftcard to that place for her. For small gifts, I recommend candy (or her favorite health food protein bars/drinks), giftcards in small amounts, mini calendars, bookmarks, and earrings/necklaces. Finally, depending on your relationship to the teen girl, you may speak with her parents or friends to determine a more meaningful or needed gift. For example, if she is getting an iPod for Christmas from her parents (and you will be seeing her after she receives the iPod), you can give her a giftcard to iTunes. If you know that she doesn't have her ears pierced, you will not give her earrings, etc.