I´ve just finish one example. There are 3 Arduinos, one master and two slaves.
The slaves have a led in their pin 13.
The control of switch on/off is with 2 buttons from Master.
Here you can see a photo:
And the video working:
A diagram of the protocol:
It´s based on a proffesional machine: http://www.cdautomation.com/download/ENG_L_M_FUJI_RS485_COMM_for_FRENIC-Mini.PDF
It´s important the lenght of the conecttion from transceiver (MAX485 or 75176) to the bus be as short as possible. I always do my connections like the photo (black and white are the bus).
Now, It´s easy do my own functions to control an arduino network. I´ve prefered use something based on a professional machine, because for sure my applications will be easiers.
To see the data in the bus,you can use RealTerm http://realterm.sourceforge.net/
. It´s free and you can see hex and ascii data.
You can see the code of this example ==> http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1245014666/15#15