A nifty web tool here allows you to shade states (or countries) on a map. You can mark the states you’ve visited, construct an electoral map, or whatever.
For the record, I’ve visited 39 states (counting D.C.)–all but the following:
AK, AZ, HI, ID, ME, NV, NH,OR, RI, UT, VT, WA
Via PoliBlog.