Hi Adarn, I live in Boulder and tour as well.

One obvious choice from home is the "Grand Loop" - Boulder - Estes Park - Grand Lake/Granby - Idaho Springs - Rollinsville (or Golden) - Boulder. (or in reverse) This can be done with a number of variations on the front range side depending on your preference for suburban riding vs more climbing, and in 2 to 4 days, and can be done as a camping or indoor (hotel/hostel mix) tour. Although the milages for a 4-day loop are moderate (~50/day), if you are carrying gear it's still challenging as there is a lot of climbing. Try to arrange to ride over Trail Ridge Road on a non-weekend / non-holiday.

There are possibilities from Frisco as well- I haven't worked out how a tour of that length can loop out around there, but you could start by looking at the "Copper Triangle" route and add out-and-backs from the "Triple Bypass." Leadville has a great hostel, if you end up there.

Farther from home, there's the San Juan Skyway - and add a side trip into Mesa Verde National Monument if you have time.
http://www.byways.org/explore/byways/2101/travel.html

If you can extend your time to more like 8-10 days, this loop (Gunnison - Lake City - Creed - Pagosa Springs - Durango - Silverton - Montrose - Gunnison) is fantastic.

This only scratches the surface of bike touring the mountains here. There are a couple of books that you can use to string things together. I like "Cycling Colorado's Mountain Passes" by Kurt Magsamen, and have but don't prefer "Road Biking Colorado - the Statewide Guide" by Michael Seeberg. You are welcome to take a look at my copies of these if you want.