As a fun weekend project or something to share with others, the following "beatbox" project by the Cortical Cafe is a great example of what can be done with minimal parts. The concept of a beatbox is to receive a series of beats, and then replay them from memory.
This example has the capability for three different tones, each of which have their own simple capacitive-sensing "button" used for entry - in this case, alligator clips. However it works quite well, as shown in the following video:
For complete details on how to make your own version, visit the project website. And for more, we're on twitter and Google+, so follow us for news and product updates as well.
If you're new to Arduino then a great board to start with is our Freetronics Eleven - the Arduino-Uno compatible with low-profile USB socket, onboard prototyping space and easy to view LEDs:
