I would say that in a typical large company (computer, biotech, financial), most employees arrive in the office between 8:00 and 9:00 and leave between 5:00 and 6:00. But perhaps 5-10% will arrive at 6:00, and 10-20% will stay past 7:00 in the evening. Off-site lunches can easily exceed an hour and a half. Many people also work at home, either reading email (managers) or working on their projects (engineers), even during weekends.

Also it is not unusual to take an afternoon off for a dentist appointment, and Elk Fever is a frequent excuse for absence during hunting season.

The technicians (lab bench workers, system operators, phone support people) have more tightly constrained hours, but practically every organization has some form of flexible time. Retail workers have even wierder schedules, usually involving some sort of rotating shift system so that our typical 7-days-a-week, 12-hours-a-day opening hours can be covered.

My limited experience in Europe is that the working environment there is more structured than in the U.S. People here work 45-50 hours a week, but not on a fixed 8 to 5:30 schedule.