Teensy 2.0 Development Board

From the shop's description

The Teensy USB Development Board is a complete USB-based microcontoller development system. Only a standard Mini-B USB cable (sold separately) is needed to connect to a PC or Macintosh. This version has solder pads for all I/O signals. The Teensy is also available with the header pins to plug directly into a solderless breadboard. All Teensy boards are shipped assembled and fully tested. Pins Teensy 2.0 has a total of 25 input/output signal pins. 22 are easily accessible when used with a solderless breadboard.This pinout reference card comes with Teensy 2.0. Pinout Card Files: Front Side (PDF) / Back Side (PDF) Technical Information ATMEGA32U4 Datasheet RoHS Certificate of Compliance Dimensions Schematic Component Locations