Now that I am done with Robogator I will continue my learning process with the next suggested robot: The Color Sorter.
Meanwhile, this is a different ( and better ) version of the same idea, a robot that sort balls related to their color.
You can read the instructions to build a similar version of it using the NXT 2.0 set at http://mindstorms.lego.com/en-us/news/readmore/default.aspx?id=142283