For those interested in pushing the limits of an Arduino, working with sound or just want something different to do, check out the tutorial on Arduino sound synthesis by Jon Thompson. He covers all manner of sound-generation techniques including PWM, the R-2R resistor ladder method of making a digital-to-analogue converter, wave-table playback and a lot more.
It is surprising what you can generate with Jon's methods, and with his notes about waveforms, additive synthesis and morphing them together you'll be creating all sorts of sound effecets in no time at all. To get started with this fascinating topic, visit Jon's tutorial. And for more, we're on twitter and Google+, so follow us for news and product updates as well.