Alaska also has sand dunes. They are in the northwest corner of the state. Very fw people ever go there.
My top locations would be:
Alaska
Wrangell St. Elias - Make sure you get into the park a ways. Gota love Alaska bush pilots
Kenai Penninsula
Denali NP - WOnder lake is neat; however, get a flight onto the Kahiltna or Ruth Glacier. Talkeetna Air Taxi regularly flys photographers onto the glaciers. If you're experienced at glacier travel, have them drop you off and pick you up later. See the mtns lit up by the low angle northern sun is almost spiritual (and I'm an agnostic!)
Lake Clark National Park
Glacier Bay - Kayaking is better than the silly cruise ships. Also make sure to wonder around above haines and skagway. Just into Canada from skagway is a little village called atlin. I could spen another month there.
The coast of SE Alaska and B.C. is hard to get to. However, the interior of B.C. is like heaven.
Someday I'm going to make it to gates of the arctic and katmai.
Canada
As mentioned above. B.C. is awesome. The border with Alberta is home of some of the nicest scenery on earth. I never tire of Banff and Jasper; however, tons of people to deal with. Glacier (not Montana), Yoho, and kootenay are good alternatives. Banff and Jasper are great after the summer holiday is over.
Can't forget Pacific Rim NP on Vancouver Island. Take the time to hike the West Coast Trail. I'd love to go back tih my 4x5.
Pacific NW U.S.
Olympic NP - Hurricane Ridge and the Hoh rain forest are must-see spots. Several beaches were also really nice. Somebody here probably knows the names as I've forgotten them.
Cascade NP and area around. Mts. Baker and Shucksan are great. You could spend a week on hwy 20 as well.
Mt. Rainier - Another busy place. I think the best way is to hike from the higher elevation ranger stations. One of the best (IMHO) was from paradise. This is also where they start climbing to the summit.
Crater Lake and St Helens are good too. I can't see spending more than a day at St. Helens. Crater lake deserves a week or more.
California
I really like the area around Shasta and Lassen. Shasta is really nice in the winter and spring. Bumpass hell and kings creek area in lassen are great. My best images from Shasta are from the hwy going East away from Shasta.
The sierras, owens and panamint, and death valley all deserve a good portion of your time. I love early fall in the sierras as everyone has gone home. Fall and spring are best for owens, panamint, and death valleys.
I haven't spent much time at redwoods NP; however, I've seen some great images from the Ca. Coast. When I move back west I'm going to spend some time there.
North American Deserts
Great Basin - One of my favorite places (yes, I have lots of them) is great basin NP. Some beautiful images from partway up the wheeler peak trail. Mt Charlston above vegas is nice. As is the valley of fire. Further north the salt playas along I80 going to SLC are really neat.
Colorado Plateau - This area deserves a year or more to itself. Can you say Zion, Bryce, Arches, Canyonlands, Capitol Reef, Grand Canyon, Monument Valley, Goosenecks (personal fav), and Canyon de chelly? I got one of my masters at NAU and wish I had stayed.
Southern Deserts - Sometimes referred to as mojave desert. Joshua Tree and the large dune fields outside of el centro are great. Mojave national scenic preserve is also worth visiting. You'll like the Kelso dunes near there. The Dumont dunes are also nearby. Not far from baker. Also lumped in here is Saguaro NP. This is another neat place. Lot of opportunities to photograph the classic Saguaro Cactus. Along the border and going into Mexico is a bunch of neat stuff too.
Baja Ca. - The drive to the tip of Baja is really nice. Mulege on the Sea of Cortez is a great place to stop as well.
Rockies
Northern - Glacier, Yellowstone and the Tetons. However, there's alot more neat places to visit. The sawtooths are a hidden gem. They won't be for much longer though. Ketchum wants to be the next Aspen
Mid - When I was sixteen I moved to RMNP. Spent several years there and loved it. Estes Park, the gateway town has grown a bit. Colorado has a bunch of other hidden gems.
Southern - I've never cared for New Mexico. However, Guadalupe mtns and Big Bend are neat places to visit. White sands is pretty cool too. I'm much happier up near four corners though.
Great Lakes
I currently live near lake michigan. Theres some neat stuff around here. The UP of Michigan is really cool. I'm off to Isle Royale in a few weeks. Along the west coast of Lower michigan is some really neat national lakeshores. However, I don't care much for the Indiana Dunes National Lakeshore.
Well anyways, these are my picks off the top of my head. I'm sure that I'll think of more later.