I really wanted to create my own iPhone app, and this is the result! It contains a pretty listing of Rubik's Cube speedcubing algorithms.
Developping this app was not too much fun, and it was even less fun to submit it to the iTunes Store due to the unbelievably complicated and buggy process. However, the frustrations it caused me were worth it in the end, because less than one year later, it has now been downloaded more than 1000 times, and made me more than 1000 dollars in income! :) The app is now downloaded on average about 7 times a day.
I am now planning to develop another iPhone app, which will be a much bigger undertaking, including some server-side scripting in PHP.