Features:
Support for uno IDE 1.0+ (OSX / Win / Linux)
Power via USB or External Source - 5V or 7 -35V (automatic selection)
On-board 500ma 5V Regulator
Built-in USB(and serial debugging)
6 I/O Pins (2 are used for USB only if your program actively communicates over USB otherwise you can use all 6 even if you are programming via USB)
8k Flash Memory (about 6K after bootloader)
I2C and SPI(vis USI)
PWM on 3 pins (more possible with Software PWM)
ADC on 4 pins
Power LED and Test/ Status LED (on Pin0)
Weight: 4g