"Just a note: sometimes the disability is not readily apparent."

Here in Maine you are required to have either handicap plates or a placard hanging from your rear view mirror, regardless of your disability, to park in a handicap space. We even have special parking spaces (right next to the handicap spaces) for expectant mothers in a lot of mall and grocery store parking lots in the Portland area.

I tend to park off in the corner somewhere because A) it forces me to get in a short walk and B) people are less likely to ding up my car.