The Teensy 3.0 is a cool little dev board. It’s Arduino-compatible (from a software perspective, anyway), breadboardable, and only about $20US.
It also runs a 48MHz, 32-bit Arm processor, making it not only easy to use, but a speed demon. If that’s not enough, it can be overclocked to 96MHz reliably enough that this is left as an option in the Arduino plug-in code provided with the board.
Like all Arduinos, the Teensy can be programmed from the Arduino IDE, although the various differences mean that you’ll need the Teensyduino mod before you can get up and running. Install the latest Arduino IDE first, then Teensyduino.
With additional features such as digitalWriteFast(), the high speed of the Teensy 3.0 can be put to use. Within a few minutes of setup, I had an I/O pin toggling at speeds as high as 50MHz.
Dev boards like this can come in handy for all kinds of projects. A board like this has the horsepower to handle color displays with complex graphics, autopilot and other control-system-type computations, and many other tasks — even simultaneously.