The Arduino Nano is a small, complete, and breadboard-friendly board based on the ATmega328 (Arduino Nano 3.x) or ATmega168 (Arduino Nano 2.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.
 
 
Microcontroller: Atmel ATmega168 or ATmega328
Operating Voltage:5V
Input Voltage:7 - 12 V (5V model)
Digital I/O Pins: 14 (of which 6 provide PWM output)
Analog Input Pins: 8
DC Current per I/O Pin: 40 mA
Flash Memory 16 KB (ATmega168) or 32 KB (ATmega328) of which 2 KB used by bootloader
SRAM: 1 KB or 2KB
EEPROM 512 bytes (ATmega168) or 1 KB (ATmega328)
Clock Speed: 16 MHz