It's blue! It's thin (0.8mm)! It's the Arduino Pro Mini 328! SparkFun's minimal design approach to Arduino. This is a 5V Arduino running the 16MHz bootloader (select 'Arduino Duemilanove w/ 328' within the Arduino software). The Arduino Pro Mini doesn't come with connectors populated so you can solder in any connector or wire with any orientation you need. The Arduino Pro series is meant for users that understand the limitations of system voltage (5V), lack of connectors, and USB off board.
We recommend first time Arduino users start with the Uno. It's a great board that will get you up and running quickly.
To minimize the cost of an Arduino, the Arduino Pro Mini is like the Arduino Mini (same pin out) but to keep the cost low, uses all SMD components, made it two layer, etc. This board connects directly to the FTDI Basic Breakout board for programming and supports auto-reset.
The latest and greatest version of this board breaks out the ADC6 and ADC7 pins as well as adds footprints for optional I2C pull-up resistors!