Yes, it started on Friday, April 16th, but it goes until April 24th, so don't miss your chance to get out to your favorite national park this week FOR FREE. That's right, all 394 national parks are waiving their entrance fee until Sunday, so you still have one more weekend if you can't manage a weekday trip. It's all part of National Park Week, brought to you by the National Park Service.Or you could stay home, pay the small fee on a weekday/weekend that's way less crowded, and avoid the mayhem of the big parks.