8: Grand Teton - see The Tetons in Brief.
7: Cuyahoga Valley
6: Rocky Mountain - I've been near this park, not sure if in it.
5: Olympic - only seen it from a distance and from the air.
4: Yellowstone - see Accretionary Wedge: A Time Warp!
2: Grand Canyon
1: Great Smoky Mountains [NOTE: I corrected the spelling on this one!]
10: City of Rocks NR, Idaho
9: Cumberland Island NS, Georgia
8: Florissant Fossil Beds NM, Colorado
7: Chiricahua NM, Arizona
6: Tonto NM, Arizona
5: Dry Tortugas NP, Florida
4: Katmai NP & Preserve, Alaska (I would like to see this one.)
3: Kalaupapa NHP, Hawaii
2: Hagerman Fossil Beds NM, Idaho
1: Russel Cave NM, Alabama
Haven't seen very many on the most visited list, none on the least visited list. Hmm...