The Visited States Map
I broke this down into two maps. The first map shows all the states that I can remember setting foot in, including ones that I either just drove through or had a stop at the airport.
States that I have set foot in:
The only one that I don't recall specifically is New Hampshire, but I'm sure I've travelled through it since you can't get to Maine via land in this country without going through New Hampshire.
States that I've visited:
Of these, Tennessee is probably the weakest, since we only stayed there long enough to purchase a new car through a pre-arranged transaction.
create your own visited states map or check out these Google Hacks.