While my friend from Montana was here, we decided to visit the local Museum of Western Colorado (though actually I think they renamed it recently to something more self important and pretentious). It's not a huge museum, but they have a pretty darn good gun collection.
Colorado's own (alleged) cannibal, and who those wacky hippies at University of Colorado in Boulder named the school cafeteria after.
They usually have the Gatling Gun that was at Ft. Crawford, but apparently it was out the day we visited. Despite that, it was a very enjoyable way to spend a morning.