Pighixxx, from the Arduino forum, has created several pinout diagrams for the Arduino UNO and for several ATMega microcontrollers, such as the ATMega 328 and the ATMega 1284p.
These diagrams provide a clear picture about how to use each pin of the board and can be used as real “cheatsheets” for your own DIY projects. You can download them from here. Enjoy!
via Arduino Blog http://arduino.cc/blog/2013/02/10/useful-arduino-atmega-microcontrollers-pinout-diagrams/