There is more to PWM from your Arduino than just adjusting LED brightness, and one alternative use has been demonstrated by Instructables user 'recwap', who demonstrates how to control 12V DC cooling fans. These are the type found in device enclosures and can be quite inexpensive. You can use PWM to control the speed of the fans even with an external power source, and would be great for adding a thermostat-controlled cooling system or a soldering fume extractor, or just for fun - for example:
Furthermore the circuit keeps the digital outputs from the high-current fan circuitry, protecting your Arduino. Find out more from here. And for more, we're on twitter and Google+, so follow us for news and product updates as well.
The package includes a wide variety of parts, sensors and modules including: a servo motor, lights, buttons, switches, sound, sensors, breadboard, wires and more. Furthermore a Freetronics Eleven Arduino-compatible board is included to make this an extensive hobby experimenter, inventor and starter kit. However we don't leave you alone to figure it all out, included is a great project and instruction booklet, plus access to a supporting web page and software examples. In other words - this is everything you need to get started for a fun range of electronics and Arduino related projects!