Digispark ATTINY85 USB Development Board

Features:

Support the Arduino 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)
6I / 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)