The Digispark is an Attiny85 based microcontroller development board similar to the Arduino line, only cheaper, smaller, and a bit less powerful. With a whole host of shields to extend its functionality and the ability to use the familiar Arduino IDE the Digispark is a great way to jump into electronics, or perfect for when an Arduino is too big or too much.
The Digispark is shipped fully assembled except for the two included and easy to solder headers.
Specifications:

• Support for the Arduino IDE 1.0 (OSX/Win/Linux)
• Power via USB or External Source – 5v or 7-35v (12v or less recommended, automatic selection)
• On-board 500ma 5V Regulator
• Built-in USB
• 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
• Software and drivers:
• Wiki For DigiSpark http://digistump.com/wiki/digispark
• Connection And Driver Setup Tutorial http://digistump.com/wiki/digispark/tutorials/connecting

Package include:

• 1 piece digispark attiny85 1 set of header pins