Here is the current iteration of my Arduino Irrigation Controller rig:
I now have 2 of the 3 Relay Shields connected to the ADK with Ethernet. Did I say connected? It's a bit fragile to say the least. Don't breathe on it! Those green wires going into the middle of the Relay PCBs are basically held their by the tension of the wires wanting to straighten out.
I really wish the Seeeduino guys had put on those extra long headers and pins on these Relay Shields like on the Arduino Ethernet Shield. It's basically impossible to attach them to the Arduino board or the Ethernet Shield because these huge freakin' pins from the screw terminals extend 2mm out the bottom of the board (and cause shorts against tall components, if you're not careful).
Now I'm waiting on some parts from AdaFruit so I can connect the 3rd Relay Shield and create a more reliable connections to the first two boards. But, where am I going to put Relay Shield #3? Hmmm...
One other thing that confuses/frustrated me with the Relay Shields is that they cannot run off USB power (5v), you have to plug them into their own 9v power supply, or plug the Arduino into a 9v+ power supply and route the Arduino's 9v pin (not the 5v pin) and ground to the Relay Shields. That's a bit annoying. The important thing, though, is that it works. On to the next stage.