There are a lot of great outfitters in Steamboat, but the one that jumps into my mind is Bucking Rainbow. Located in the heart of downtown it is your one stop shop for so many things; fly fishing, rafting, tubing. Their staff know everything about these subjects, their guides will get you that giant fish you desire any time of year.
I love their clothes! They have great stuff in there, like all of the best styles of MissMe jeans, and super cute dresses! This is definitely a great boutique that is hidden by the fly fishing tours in the front. If you haven't checked it out already, you need to!