Just stumbled across this pedalboard-layout-planning website today:
http://pedalboardplanner.com/
It appears to still be in its infant stages (no Barber pedals listed--yet--and doesnt' work with IE) but it's about time somebody has designed a web-app for this. I think some people would find it quite useful, especially if you're like me--just about to order a board, wondering how your pedal layout will look when finished.