1. Support for the Arduino IDE 1.0+ (OSX/Win/Linux).
2. Power via USB or External Source - 5v or 7-16v (automatic selection).
3. On-board 150ma 5V Regulator.
4. Built-in USB (and serial debugging).
5. 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).
6. 8k Flash Memory (about 6k after bootloader).
7. I2C and SPI (vis USI).
8. PWM on 3 pins (more possible with Software PWM).
9. ADC on 4 pins.
10. Power LED and Test/Status LED