One on the largest challenges in music is learning the various rhythmic patterns of classical piano songs you're attempting to learn. The largest challenge of life is to be entertained by quality.
For all the crap out there, there's sadly a lack of high quality and intellectual entertainment: enter Touch Pianist.
You can use it as a web application, an Android app, or an iPhone app.
The basic concept is that by pressing any key on your keyboard or tapping your phone, you can play the next note or chord in the melody of a boatload of classical songs. You can also enable "watch" mode where you can listen and look to help learn the rhythms and timing.
Wham. Suddenly I'm a master of the piano thanks Batuhan Bozkurt, who created this thing and several other crazy musical apps that you can toy around with at EarSlap.com.
Here's just a sampling of the composers who's songs are available:
Go spend a few minutes toying with this thing. It's pretty nifty, and if you like it, snag it for your smart phone and tell me how it is, because I still have a flip phone like a real boss.