I was at a beer festival Saturday that was comprised of only Colorado Breweries and left realizing how spoiled we beer drinkers are out here. Off hand there are a few that I love: Upslope, O'dells, Pug Ryan's, Broken Compass, Boulder Beer Company, and probably a couple more. Upslope Lager is tough to beat and I think they have a decent distribution network.
I tried quite a few Kolsch style beers which is sort of like a lager but with more citrus notes. Great for summer.
The only beer that I truly miss from up north is Premium Grainbelt as it is not distributed out here and to me is an amazing "crappy" beer.