Adafruit USB Boarduino (Arduino Compatible) Kit (w/ATmega328)

If you've ever struggled to use a solderless breadboard with an Arduino, you understand how frustrating it can be! This development board acts just like an Arduino, and works with the latest Arduino software. For many projects it can even be preferable! The kit includes all parts necessary, the assembly is straightforward and well documented, using just a soldering iron anyone can complete it within 10 or 15 minutes. This version of the Boarduino does not have a DC jack. That means you can't use a 9V adapter or battery holder with it (unless you build a 5V power supply). However it does have USB built in and you can power your project or USB or by using a Mintyboost kit (which takes 2 AA batteries). Specifications:

• Designed to plug into a breadboard for easy prototyping
• Petite size, only 2.75" x 0.8" (75mm x 20mm)
• All 'standard' pins are brought out - Digital 0-13, Analog 0-5, ARef, 5V, 3V, Ground, and Reset
• Chip comes pre-programmed with a "no-wait" Arduino bootloader (Read more here)
• 4 LEDs! There's a green power-good LED, a red "pin 13" LED (just like the Arduino), and a pair of RX and TX indicator LEDs for debugging the serial connection
• Nearly-all-surfacemount design. We left the chip as through-hole to make it easier to upgrade and repair. All surface mount parts are pre-assembled and tested.
• Reset button
• ATmega328P, running at 16.00 MHz, just like all Arduinos
• 6-pin standard ICSP header
• USB miniB jack
• 500mA fuse protects your computer's USB port from overcurrent
• Auto-reset capability

There's a lot more to read at the USB Boarduino webpage.