Arduino Nano is a surface mount breadboard embedded version with integrated USB. It is a smallestcompleteand breadboard friendly. It has everything that Diecimila/Duemilanove has (electrically) with more analog input pins and onboard +5V AREF jumper. Physicallyit is missing power jack. The Nano is automatically sense and switch to the higher potential source of powerthere is no need for the power select jumper.
Nano’s got the breadboard-ability of the Boarduino and the Mini+USB with smaller footprint than eitherso users have more breadboard space. It’s got a pin layout that works well with the Mini or the Basic Stamp (TXRXATNGND on one toppower and ground on the other). This new version 3.0 comes with ATMEGA328 which offer more programming and data memory space. It is two layers. That make it easier to hack and more affordable.
You end up paying less with Nano than Mini and USB combined!
The Arduino Nano can be powered via the mini-B USB connection6-20V unregulated external power supply (pin 30)or 5V regulated external power supply (pin 27). The power source is automatically selected to the highest voltage source.
See your Arduino Nano build!
Arduino Nano 3.0 Assembly from Gravitech on Vimeo.