The long-awaited Arduino Due is now available. This device, featuring an Atmel SAM3X8E ARM Cortex-M3 CPU, is a huge generational leap for the Arduino platform. Using the same footprint as the Arduino Mega, the Due is faster, has more memory and more I/O than any previous Arduino, and puts it on a par with the Maple, Netduino and other similar platforms.
You can check out the details here.
I was able to recently purchase one through the Maker's Shed, although supplies seem to be somewhat limited. This board, combined with the new Arduino 1.51 beta, led to my first Due-based Blinkie Lights sketch today!