When I lived in Atlanta and worked late theatre hours, we'd often make 3am or 4am trips to the 24/7 Home Depot for more lumber or miscilanious supplies.  There was never a big crowd at 3am, but the people who were there wern't the normal Home Depot customers - they always seemed to be there out of desperation.

One time we showed up around 3am to buy a lot of lumber.  When we went to check out, we had an enormous rack of it in our cart.  The cashier had just started to ring us up when I noticed there was someone behind us in line.