Did you know that the Utah Museum of Natural History has free admission the first monday of every month? You can't beat free!
I found this and other fun activites and offers at gocitykids.com. You sign up and they send you a newsletter with all sorts of fun things. Their website also has a feature where you can enter your child's age and what sort of activity you are looking for (fun, educational, etc.) and it shows you everything in the area. You can choose your location, so I imagine they have similar information for areas across the country for my far-flung friends!
Thanks, Kat for the heads-up!