For what you might pay a live teacher for a handful of lessons, you can buy Ion Audio Piano Apprentice for iPad, iPod, and iPhone, and learn to play piano whenever it's convenient for you.
The Piano Apprentice is a 25-note keyboard with built-in speakers. Download the free Piano Apprentice app and install your Apple mobile device on the Apprentice, and the screen will show you a professional piano teacher's hands placed on the keys where yours should be.
If that's not clear enough for you, the correct keys for whatever you're supposed to play light up as well. This appcessory makes for an inexpensive piano teaching tool, especially when coupled with the iPad's large screen.
Availability: IonAudio.com | $100, or from reseller Zzounds for as little as $60.