Coming April 21-29, 2012. Get ready because everyone of the 397 parks in the US National Park System will have free admission for the entire week. Yep, that means you can go everywhere from Acadia, American Somoa and Arches to Yellowstone, Yosemite and Zion all for free. It’s a great time to check out all the volunteer opportunities at the parks too. This is really one of the best values in the US.