Play with virtual Lego blocks and create your own plans!
This is Lego's official (discontinued) brick design program. With it, you can build your own sets within the editor and paint the pieces any color you wish.
Afterwards, you can generate step-by-step building plans and print them out. Or you could place your creation into a desert background and take a picture of it to share with friends.

This program runs extremely well on RPi. The only problem I (Botspot) could find was the sound effects don't work.