If you're looking for something fun to make and to annoy others with, consider making your own ping-pong ball launcher. Enthusiast Franciso Dias has described his own version to almost infinite detail, including publishing all the files required to make the launcher parts with a 3D printer and the base with a CNC or laser-cutting machine. The balls are propelled by two counter-rotating wheels, and the angle of launch is controlled via servos. Here it is with a quick launching:
With some scaling of dimensions you could also create a launcher for larger or smaller balls, such as baseballs or cricket balls. Nevertheless for the complete details click here. And we're on twitter and Google+ - so follow us for news and product updates as well.
If this sort of project intrigues you and you're new to Arduino, the first step is a solid board for your projects - our Freetronics Eleven - the Arduino-Uno compatible with low-profile USB socket, onboard prototyping space and easy to view LEDs: