the schematic is created in eagle and eagle is a free cad software
i have also uploaded an image of the mega schematic that is from that download.
I do suggest, however, that you get eagle. if you are playing around with arduinos, you will inevitably be making some sort of schematic some time.
there is also a more introductory software that you have parts and connect them visually and it will build the schematic. the name escapes me right now but its what ladyada uses in her tutorials. check her page out.