The classic Arduino Nano is the smallest board to build your projects with.
Breadboard-friendly board based on ATmega328
Works with a Mini-B USB cable instead of a standard one
The Arduino Nano is a small, complete, and breadboard-friendly board based on the ATmega328 (Arduino Nano 3.x). It has more or less the same functionality of the Arduino Duemilanove, but in a different package. It lacks only a DC power jack, and works with a Mini-B USB cable instead of a standard one.
Item Specifics Microcontroller: ATmega328 Architecture: AVR Operating Voltage: 5 V Flash Memory: 32 KB of which 2 KB used by bootloader SRAM: 2 KB Clock Speed: 16 MHz Analog IN Pins: 8 EEPROM: 1 KB DC Current per I/O Pins: 40 mA (I/O Pins) Input Voltage: 7-12 V Digital I/O Pins" 22 (6 of which are PWM) PWM Output: 6 Power Consumption: 19 mA PCB Size: 18 x 45 mm Weight: 7 g