Cooling the Server Room?

kolchak asks: "As the Australian summer heats up, we are looking at a cooling solution for our computer room. We have 4 racks (almost all full) with around 40 machines, switches, routers, 2 UPSs and 2 monitors. Unfortunately, its located in the middle of the office with no windows available for ventilation. We can vent the exhaust into the ceiling space which in turn is vented outside. Also, since the room is so small, we need to install any cooling device outside the room (a store room backs on which will house the cooling unit and potentially pipe hot / cold air through the wall). All the units we've seen so far need to be in the room, we just don't have the space. Anyone come across and solved this? Any ideas on good cooling units we can install easily and cheaply?"