I'm to the point in my own project (Array of Optoisolators - http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1204135553/6) where I'd love to collaborate with others and get some prototype boards built. More specific forums for this would be great!
These projects are beyond the scope of an Arduino tinkerer, so they shouldn't be mixed in with, say Freqently-Asked Questions!
That's a good idea, and I'd thought of a relay board. I hadn't thought that far ahead, but it's probably a good idea to have optoisolators between the Arduino and relay coils too 