This Fritzing project is a first try for a special DMX shield. The Arduino sketch is currently not released - this will be done soon.
It has two DIP-switches for configuration (serial speed, serial echo, ...) and connectors for a 3-way switch for mode setting to ON/PROGRAM/OFF.
Also there are connectors for a potentiometer for setting the master light level and connector for a 2*3-way switch for cross changing the RS485 output.
The Arduino software has a small serial parser for setting DMX values. The goal is that you can set up a time and target values for DMX channels and the Arduino does the fading to the target levels "in background".
Another feature is the use of a 23LC1024 - a 128kByte SRAM accessable via SPI. Currently it is not used but future version will use this option.