The LeoStick is a tiny breakout board for the ATmega32u4 MCU that will be used in the forthcoming Arduino Leonardo. We're shipping it with a modified pre-release version of the Leonardo bootloader, so you can pop it into your USB port and load sketches right out of the Arduino IDE. The USB plug is part of the PCB so the whole thing is really tiny. It's hard to get a concept of how small it really is by looking at photos, but perhaps this will help give some perspective:
It's the size of a typical USB memory stick! I spent many, many late nights labouring over Eagle laying out the PCB trying to cram it all into the smallest space possible, and it's a seriously tight PCB. After long sessions working in Eagle with everything zoomed way in close I'd start to lose perspective on just how small it is, and every now and then I'd have to sit back, print out a hard copy of the PCB at 1:1 scale, and re-orient myself. Part of the reason for the cram-job was because we kept coming up with ideas for new features to add to it, so this isn't just equivalent to a full-size Arduino: it does more than a typical Arduino. Check this out:
We combined the power, TX, and RX LEDs onto different elements of a single RGB LED, which gives a really cool effect with the colour changing as you communicate with it via USB. We also replaced the normal single-colour LED connected to pin D13 with an RGB LED, so you not only get the usual red output on D13 but you also get green on D9 and blue on D10.
Then we added a Piezo module on the bottom so you can play sounds directly from the LeoStick without having to plug anything else in. It's ready to produce RGB light and sound output straight out of the box.
We're really proud of the end result, and there are already a bunch of people doing cool things with it. Within hours of them being distributed at linux.conf.au there were people using them to do things like play the "Raiders of the Lost Ark" theme on the Piezo speaker, and even to create a Morse code sender that takes text messages via the serial console and outputs them as Morse. We also saw one that had the connection to the Piezo cut and remapped to an analog input so it could be used as an input device to detect knocks and claps.
We can't wait to see what other things people do with the LeoStick, so please check it out and share your projects over on our forum!