io9 tried to separate the urban legend laws from ones actually on the books, verifying the laws from a few reliable sources.
In their research, they found that in Nebraska, you can't get married if you have gonorrhea. And that in Iowa no kiss may last more than five minutes.
Another Nebraska law reportedly on the books: Couples sleeping at a hotel must wear the clean, cotton nightshirt provided by the hotel, even when they are having sex. (HG.org)