Arduino Nano is a surface mount breadboard embedded version with integrated USB. It is a small, complete, and breadboard friendly. It has everything that Diecimila/Duemilanove has (electrically) with more analog input pins and onboard +5V AREF jumper. Physically, it is missing the power jack. The Nano will automatically sense and switch to the higher voltage source of power, there is no need for the power select jumper.