All the features of the Arduino Leonardo at a fraction of the size! The Arduino Micro is quite versatile as it's big enough for breadboard prototyping, but small enough for permanent installations.
The Arduino Leonardo now has a kid brother based on the same ATmega32U4 chip! The Arduino micro is an itty-little-bitty development board that comes fully assembled and ready to go out of it's cute little box. It has 20 digital input/output pins (of which 7 can be used as PWM outputs and 12 as analog inputs), a 16 MHz crystal oscillator, a micro USB connection, an ICSP header and a reset button. The micro can emulate a mouse and keyboard, in addition to a virtual (CDC) serial / COM port when connected to your computer, so have some fun with it!
You can find more details on the getting started page.