I have been experimenting with using the Arduino to receive DCC commands in order to use small dedicated DCC decoders to operate animations and other non-locomotive things on my modular layout.
Thanks to a posting by Geoff Bunza on the MRH forum. In that article Geoff describes how one can build a small decoder that can be used to trigger up to 17 discrete events. I have details about my experiments with this project here: http://www.trainelectronics.com/DCC_Arduino/
The next logical step is to create a dedicated DCC controller that can be used to trigger events. I found this listing http://railstars.com/software/cmdrarduino/ and have been testing the Arduino libraries and code with great success.