To enable easy documentation of pin assignments, BusyDuckMan created a couple of ASCII art of Arduino Uno and Mega boards marking ports, PWM and coms. You can now then simply copy and paste as a comment into your code and document in an easy way how the arduino is connected to other devices:

They can be pasted into code comments, (use /* and */ in the arduino IDE to create a block comment). They can also be useful in forums, when you need a quick arduino diagram, but don’t want to fire up an image editor.