For something that is completely different to the usual projects, and also incredibly imaginative, check out the following "Smart Coaster" by Mario Lukas. It not only protects delicate surfaces from hot drinks - it can also determine what sort of drink it's holding and more. Using a temperature sensor and pre-programmed temperature levels the coaster can sense the temperature and illuinates a string of LEDs around the coaster to indicate the type of drink. The enclosure has been laser cut for accuracy and overall appears to be a well-finished end product, for example:
If you need a tiny and convenient Arduino-compatible to embed into your next project, check out our Freetronics LeoStick. It's the Arduino Leonardo-compatible board that's cheaper and smaller than the original:
Apart from being one of the smallest Arduino-compatibles on the market with USB, it also has an onboard RGB LED and piezo which can be used a knock sensor and various tune and sound effects. Plus you can add extra circuitry with the matching protostick! For more information and to order, click here.