Here you can find some of the designs made by David Sjunnesson from 1scale1. All are Open source and free to use for Non commercial applications.

DiMeX

Interface between Arduino and the DMX protocol commonly used to control stage lighting. It also has the added functionality of an wireless XBee module.

More information and file download: DiMeX

DS1307 RTC

Arduino library to control the real time clock (RTC) DS1307. Includes how to connect it and easy setup.

More information and file download: DS1307

Usefull sketches

Mixed sketches to simplify your life when working with Arduino, processing, Puredata, Twitter and so on.

More information and files download: Sketches