One for Utah:

The Energy Loop (Huntington & Eccles Canyons)
It's remote. It's out of the way and hard to get to. But it's totally worth it once you get there. My favorite ride incorporating the Energy Loop is this:

I-80 east from SLC to US-40 East to Duchesne, UT. Next, take US-191 south (Indian Canyon) to Helper, UT. US-6 to Price and UT-10 to Huntington, UT. This is where the Energy Loop begins. Climb up Huntington Canyon on UT-31. At the top, hang a right on UT-264 (Eccles Canyon). After passing the gigantic coal mine, merge left on UT-96 toward Scofield, UT. Hwy 96 runs to Colton, UT and intersects US-6 in Spanish Fork Canyon. West on US-6 to Spanish Fork and north on I-15 to SLC.

This ride includes mountain passes (5), alpine lakes and meadows, great curves/riding and minimal traffic once off the interstates. Also, there are plenty of places to camp, fish, sightsee and hike along the way.

 

I gotta try the Eccles Canyon and back to Highway 6 part of that loop sometime. I've just gone on down to Fairview and returned to 6 on 89. Based on the time I've spent between Scofield and the Skyline, I'm sure that part of the ride is great. Also, I'll vouch for the rest of the ride TheBB has laid out. It's a good 'un.

 

bumping to the top. still have some states with no replies,

 

There are too many to list. See all the threads about the mountains, Maggie Valley, Blue Ridge Parkway etc.