If you use Apple's Calendar program in OS X, then you might commonly use the various day, week, month, and year views when organizing your schedules; however, by default the day view will show you only one day, and the week view will only show you a full seven-day view.
Even though the options for seven-day view and single-day view may be perfectly fine, there is a hidden feature in Calendar which will let you view between two and six days.
To do this, simply click the Day, Month, or Year button, and then press Option-Command followed by a number in the range of 2 through 7. Doing this will switch your view to Week view, showing the number of days designated by the number you pressed. For instance, if you pressed Option-Command-3 then you will see three days shown in the Week view, as opposed to the default seven.
Note that you can also use Option-Command-1 to perform this task, but this would be the same as the day view.
Keep in mind that while you can do this, the view does not interface well with some of the Calendar's navigation controls. For instance, if you use the Command-arrow hotkey to navigate forward and backward by a week (as opposed to scrolling), then you will see the view jump ahead seven days regardless of the current view.
As a result, if you have Monday, Tuesday, Wednesday shown using this trick, then skipping ahead with the arrow hotkey will show the next Monday, Tuesday, and Wednesday.
Even with these small limitations, this can still be a fun view to have. In order to use it, however, you do have to remember to invoke it each time you switch views. If you are in this view and move to the day, month, or year views and then switch back, the week view will default back to seven days.