Saturday is the start of the National Park Service’s National Park Week, which runs through Sunday, April 29! That means free entry to Glacier and Yellowstone national parks, as well as other sites the service manages.

In addition to entrance fees being waived at parks, I’ve noticed several smartphone apps covering national parks are available for free for a limited time. I haven’t used these yet, but plan to check them out:

• Fotopedia National Parks (iOS): This app has 3,000 photographs by QT Luong from all 58 U.S. parks, plus descriptions and travel planning information.
• Chimani national park apps (iOS and Android): Chimani National Parks and apps for individual parks such as Yellowstone are available. The Yellowstone app, for example, has points of interest, trail information, an audio auto tour and more features.
• National Parks by National Geographic (iOS): This brand-new app and the first park guide download are free, but additional guides require in-app purchase. It provides  must-see features, maps and GPS coordinates, and photos that include vintage images from the National Geographic Archives.