Highwood pass is a great one, 10/10 views just like Lake Louise to Jasper is, but you can do a round trip to and from Calgary in just a few hours (I left at 7:00am and was home by 11:00am). I know it's popular with cyclists as well. Plus grab some jerky in Longview on the way.
One I'm curious about is doing the same thing,3-4 hours ish but checking out the badlands and hoodos instead of the mountains. Anyone have a good route for that? Or is that more of a whole day thing?