Hi Jim, in 2005 I did a 5 week tour in Colorado. After getting some advice from friends, I decided to plan it around the concept of "ride every paved continental divide crossing in CO" - and it worked out great.
here's a google map I tried to make of the route I actually rodehttp://tinyurl.com/2ouoay
Google maps isn't allowing the rote to go over independance pass right now - I think the application knows it's winter and reroutes! - so from point "C" on this map, what I really did is continue east and then north to leadville, then over Tennessee Pass to Minturn/Vail.
I really enjoyed my trip. I had to cut it short, so I missed out on crossing Trail Ridge Road in Rocky Mtn National Park - which shouldn't be missed, as well as the northeast passes out by Steamboat.
Pretty much, the higher the pass, the nicer the riding. There are more people/cars in the northern parts around the ski areas (i-70) and fewer in the southern loop - Gunnison, Pagosa, Durango. In addition to the higher passes, the section between Blue Mesa Reservoir and Paonia on Hwy 92 was a real treat - remote, beautiful, rolling hills.
Generally, there was enough camping and services, the roads had reasonable shoulders (with a few exceptions). Stay in the mountains, the front range is heavily populated and not really that great riding - too many cars, not enough hills.
Along with the AAA state map and the state recreation map, I used this book, it was very useful, with elevation profiles and service locations on all the major passes:http://www.rei.com/product/688722
If you have any specific questions, or need a local contact, let me know, I live in Boulder now (yes, I decided to move here partly b/c of that tour).