What are the "must see" places in Colorado and Wyoming in summer? Especially interested in Custer to Yellowstone down to Durango via Glenwood Springs. How are the Canyon cabins in Yellowstone? Any places to stay that are decent in Grand Teton area under $100?

For the Tetons, you might try Signal Mountain Lodge. The prices have escalated in recent seasons, but they might have something under $100. But it is a popular place, so it might be sold out for the summer.
I have stayed at various cabins in Yellowstone and find all of them marginal except for the Old Faithful Snow Lodge Cabins. Rooms, with a bath, at the Old Faithful Inn are fine, if pricey.
Lake Lodge hotel style rooms are ok.
But Lord deliver me from that thing at Grant Village. Some of the rooms are so small I can stand in the middle and come within an inch or two from being able to touch my fingers to opposite walls at the same time. Style wise it is totally out of character.
The so-called Western Cabins around Old Faithful are ok if you accept the conditions. At least they are better than they were the first time I went, years ago. We had to build a fire in the stove to keep from shivering in the bed and the water faucet was outside, as were the other facilities.

It is a long drive from the Tetons to Durango, but if you get that far south, there are some things to see. In Grand Junction, detour by the Colorado National Monument. If time permits, drive to the south rim of the Black Canyon of the Gunnison. In Ouray, ask for directions to Yankee Boy Basin, making sure that the road is passable.
The scenery up there is great, but that road can be a trip in itself. Some people opt for a jeep tour.
The road from Silverton to Durango is beautiful if the sun is shining. I have been over it in the fog, which is not the most pleasent way to go. Once in Durango, it is a short drive to Mesa Verde National Park.

Coming south, you might consider stopping at Fossil Butte National Monument. It contains some incredible geologic impressions of life in an ancient lake. The fossils are so well preserved that you actually see fossils of fish within fish -- obviously a little one eaten by a big one. And a detour by Dinosaur National Monument is not out of the question. Having been there I rate it as marginal to fair. It depends upon what you have seen so far in dinosaur fossils still in the original rock matrix.
In Colorado, other than what I have mentioned, I love that drive over Trail Ridge Road in Rocky Mountain National Park. But that is well to the east of a route that would take you to Grand Junction.

By the way, I hope you already have a cabin in Yellowstone. Availability was low 3 weeks ago.

You will have a hard time finding lodging in the Park or Jackson under $100 during the prime summer months. There are some tents & cabins at Colter Bay. Better call now! You might try staying on the west side of the Tetons in Idaho. The view of the Mts is not as dramatic, but prices are cheaper and it is the quite side of the Tetons. There is a ski lodge in Alta, ID. Take the ski lift to view the Tetons nearly alone from the top. Check for open days. They do not run the lift every day. NOTE: We've found the best food in the Park is at Signal Mt. And take the drive up Signal Mt for Sunset. We watched the sunset nearly alone escept for 4 other people.
There is a new lodge at Old Faithful. I stayed in the cabins at the Canyon years ago. The park accommodations are sparse. I would recommend staying in West Yellowstone. We always had a nice room for a decent price (yes, under $100). Try one of the 3 Best Westerns in town.
Many films have been made in the Custer area. Don't miss the Needles Parkway.
Ouray and Telluride are beautiful. If you have a 4-wheel drive, get a local map of 4-wheel roads. 2 amazing mt passes are Engineers Pass and Emogene Pass. Both about 10,000 ft with views to die for. You can rent Jeeps in Ouray.
Black Canyon of the Gunnison is worth the short trip off the main road. And Curecanti Nat'l Rec. Area is scenic as well.
I've been to Dinosaur N.P. You can see lots of fossils but the secret is to get off the main road and drive down some of the dirt roads to the Green River. We camped overnight on the banks of the river. At night you can see more stars than you ever thought. This is true of most of this part of the country. Enjoy your trip!

Here are just a few of the places in the lower parts of Colorado;
(CO) Black Canyon of The Gunnison Nat'l Monument (AAA Map of SW US Ref G26): http://www.nps.gov/blca/
Deep (over 2,000 feet) canyons cut into dark granite by Gunnison River. Spectacular views from lookout points. Nice but small campground. Flush toilets but no showers. Evening campfire talks by Rangers. Recommend one day. Motels in nearby Montrose.

(CO) Colorado Springs (AAA Map of SW US Ref F29):
http://colorado.com/Colorado/towns/c...ngs/index.html
A great place to visit and see local attractions: Garden of the Gods, Seven Falls, Cave of the Winds, Pikes Peak, Cog Railway, Air Force Academy etc.

(CO) Durango-Silverton (AAA Map of SW US Ref H26):
http://durango.org/. Some of most scenic views in CO. Start point (Durango) for Durango - Silverton Narrow Gage Steam Railroad: http://durango.org/durango/train.html & http://www.visitorinformation.com/durango/train.html. All day trips through canyons along Animas River. Reservations recommended. Phone: 970-247-2733.or 888-872-4607. Drive from Durango to Silverton & Ouray highly recommended. Campgrounds & motels available. Also close to Mesa Verde Nat'l Park. (MUST SEE)

(CO) Great Sand Dunes Nat'l Monument (AAA Map of SW US Ref G/H29): http://www.nps.gov/grsa/
Located in high (7,800 ft) valley, dunes rise up to 800 ft above floor. Hike up dunes but shifting sands make difficult. River flowing at base of dunes 'disappears' into sand. Hike to top considered strenuous. Hike up Mosca Pass Trail into green forest. Nice large campground. Flush toilets but no showers. Evening campfire talks by Rangers. Recommend overnight stay. Motels in nearby Alamosa.

(CO/UT) Hovenweep National Monument (AAA Map of SW US Ref H24/25): http://www.nps.gov/hove/
An out-of-the-way site in southeastern Utah and southwestern Colorado about 40 miles west of Cortez, CO. Consists of a main site and several outlying sites. Main site has small Visitor's Center and small campground. Lovely walk takes in several ruins around and within small canyon. Ranger guided walk to rock art. Outlying sites somewhat rough roads but worth visiting. Solstice markers at Holly site not marked but worth observing during solstice periods (need guide to show where located). Motels in nearby Cortez.

(CO) Mesa Verde Nat'l Park (AAA Map of SW US Ref H/I25):
http://www.nps.gov/meve/ and http://mesaverde.org/ and
http://www.gorp.com/gorp/resource/US...rk/co_mesa.HTM
Mesa Verde Nat'l Park (Colorado) (AAA Map of SW US Ref H/I25): http://www.nps.gov/meve/ and http://mesaverde.org/ and http://www.gorp.com/gorp/resource/US...rk/co_mesa.HTM
Located off US-160 in southwestern Colorado, 10 miles east of Cortez and about 30 miles west of Durango. Steep climb from highway up onto mesa area - towed vehicles not allowed past Morefield campground - parking allowed by entrance station. This is a very popular Park and summer crowds can be heavy. The best examples of early Native American cliff dwellings. Views from cliff rims and several Ranger-guided tours through ruins. Balcony House, Cliff Palace & Long House require tickets purchased at Visitor's Center (8:00am - 5:00 pm) (1998 rate: $1.75) - about 15 miles before ruins. Expect waits in line and difficulties in getting a time you want. Balcony House tour requires climbing ladders & exit via hands & knees through narrow 'tunnel'. Do it if you can stand the heights & climb.

Also see the Mesa Top Sites as they provide a history of the evolution of the living conditions prior to the actual Cliff Dwellings. Guided commercial tours available from Far View Lodge for morning, afternoon or all day. Morefield campground (open thru mid-October) has 450 sites and is almost never completely full but better sites go by noon or so. Deer wander thru cam areas evenings & mornings (do Not feed). Evening Ranger programs held at Amphitheater. Commercial Laundromat & pay showers by campground. Knife Edge Trail an easy walk. Prater Ridge Trail longer and on top of mesa. Hike up to Lookout Point strenuous but views worth it (no guard rails). Commercial camping nearby. Far View Lodge inside Park (advance reservations necessary) & Motels available nearby. Recommend minimum of 1-2 full days.(MUST SEE)

(CO) Pike's Peak (AAA Map of SW US Ref F29 - west of Colorado Springs): Famous for 'Pike's Peak or Bust' slogan of early settlers. Over 14,000 ft elevation west of Colorado Springs. Can drive up or take Cog Railroad (Manitou Springs). Drive from Colorado Springs to Cripple Creek via dirt 'Old Gold Camp Road' very scenic. From Cripple Creek to Canon City via dirt 'Phantom Canyon' road also very scenic (Not for motor homes or towed trailers). (MUST SEE)

(CO) Royal Gorge (AAA Map of SW US Ref G29 - west of Canon City): http://electricstores.com/bridge/default.htm
Wooden-planked suspension bridge 1,100 ft over gorge & river. A bit 'Touristy' but worth the visit. May walk or drive smaller vehicles over bridge or take cable car across. Breath-taking view down.

LE, all the places listed are worth visiting and are truly beautiful. As far as lodging, here's a thought -- what about CAMPING? Get closer to Mother Nature, enjoy a campfire, see the stars. At most of the Nat'l Parks, even the busiest ones, if you arrive early in the morning (by 9 am) you can snag a campsite. That's my strategy and it works every time. I've been doing it all my life. If you're flying out west, just pack as if you were going backpacking and take your pack as luggage, or pack a big cooler with camping gear, duct tape it shut and check it. Rent a car and away you go...

My strongest memory of my trip to the area is of the drive from the south to Yellowstone. We stayed at a resort not well known to non-natives, Thermopolis. I think it is a state park. It has huge thermal pools, on a large river. There are motels and restaurants there.

We also enjoyed very much a couple of days at Cody, WY, a little east of Yellowstone. They have the best wild west museum in the country there. It's HUGE. Easy to spend a fun day there. This place feels like the real West.

Within the park, I think the nicest place to stay is at Yellowstone Lake lodge. It is beautiful, and has some cabins also. But it is hard to reserve.
We did not get reservations last time, and were forced to stay at West Yellowstone. This place is an ugly tourist trap, but it has lots of motels and restaurants that will have vacancies, and is on the border of the park, close to places you will probably want to see.