Local is best - and in CO, you shouldn't have any issues stocking the shelves with beer from the area. I'm assuming the shelves aren't refrigerated?
CO:
Odell (Cellar Series/Woodcut Series)
Avery
Great Divide (YETI)
Funkwerks
New Belgium
Wynkoop
Breckenridge
Crooked Stave
Boulder
You can also go a bit west:
Rogue
Firestone Walker (Walkers Reserve, Parabola, Anny releases)
Green Flash (Double Stout)
Ninkasi
Deschutes
Sierra Nevada (Ovila)
Anchor (Zymaster Series, Small Beer)
Stone (IRS, Smoked Porter, Old Guardian, Special Releases)
Lost Abbey
The Bruery
Bear Republic
Imports Schmimports (unless you can grab up some Cantillon)