I really like Jack's idea but like others have mentioned it really is dependant on your application and how you are going to use it. In my shop I have one mounted towards the front of the shop on a wall where I can stretch it out to work on anything in the front half of my shop, whether it is near the two post lift or at one of the two motorcycle hoists.
I also have another reel mounted near the overhead door so if I am working on the rear of a vehicle I don't have to stretch the hose from the front of the shop past everything inside the shop. It also works great if I need air outside my shop door, it is right there handy on a reel.
On a side note I would also like to echo those who mentioned putting air hose connections under the front of the work top of the benches. When I first started wrenching at my place of employment each workstation had an air connection at the back of the workbench about 6"-8" above the working surface. I thought it was neat for each mechanic to have his own air outlet but after using them for a while I realized that every time I was working on a gearbox or a motor or something on top of the workbench and using my air, the coiled air hose seemed to knock each and every aerosol can, parts bin, wrench, screwdriver and ratchet off the bench and onto the floor.
I quickly decided to move the air under the workbench and low and behold, I was able to keep items on top of the workbench. When I built my home shop all of the air fittings for the benches are routed underneathe the front. I have four under a 16' long workbench and three outlets under my 8' workbench. I highly recommend it.
Mike.