Until this year, summer park-hopping sure sapped a lot of green. An ambitious seven-park circuit - say, starting at Joshua Tree, looping through the Grand Canyon, Bryce, Zion, the Grand Tetons, and Yellowstone, and winding up (exhausted but invigorated) at Glacier - could set you back $110 in entrance fees. But with the new National Parks Pass, introduced last month, visitors can blaze the same happy trail for only $50. The pass is good for a full year and accepted at all 379 national parks, from Florida's Everglades to Hawaii's Haleakala. Pick one up at any park entrance or on the Web at www.nationalparks.org, or call 888/467-2757.