Arduino Mega 2560

The Arduino Mega 2560 is a microcontroller board based on the ATmega2560. It's a fully featured Arduino board.

Needless to say, this is quite the beast. Not only that, but the crazy Arduino guys managed to make it compatible with existing shield designs. What a nice bunch of dudes to make all your existing toys work with the new design.

Overview
Specifications

* Microcontroller: ATmega2560
* Operating Voltage 5V
* Input Voltage (recommended) 7-12V
* Input Voltage (limits) 6-20V
* Digital I/O Pins 54 (of which 14 provide PWM output)
* Analog Input Pins 16
* DC Current per I/O Pin 40 mA
* DC Current for 3.3V Pin 50 mA
* Flash Memory 256 KB of which 8 KB used by bootloader
* SRAM 8 KB
* EEPROM 4 KB
* Clock Speed 16 MHz

For more documentation click here