My adventures in RS-485 communication thus far have amounted to building an internal network for my track signal controller, allowing any number of boards to chained together.
Provided, of course, that the 485 specification is respected with repeaters after the specified number of signal drains.
I have also worked on an RS-485 shield for the Arduino, as can be seen below. By using the SoftwareSerial library, it is possible to use both ports alternately, (but not together) allowing a maximum of 64 devices (32 per transceiver to be connected to the Arduino, potentially for a sort of RS-485 based router.
These were used as part of a talk (detailed on my talks page) on serial communications, culminating in a lab session where participants created their own multi-drop LAN.