Link all the calendars to Outlook, then drag/drop to copy the events into the
"master" calendar. This however won't keep things in sync, it's a one time
copy. If you want to "roll up" all your calendar events that can be done with a
Content Query web part, but it will only display in list form, not a calendar
view. Anything more than this is going to require custom programming or a 3rd
party tool.