Do Sunday brunch at the Delta in Kananaskis. You get a free swim if you do - they have an indoor/outdoor hot tub, steam room, etc. Nice relaxing way to spend an afternoon.
Banff is boring as hell unless you like tourists and tacky stores. Hike Johnston canyon if you like but continue on to the Ink pots - not as many people and a nice hike (not too difficult).
Dinner at the Calgary Tower is cool - make a reservation and get elevation for free.
Drumheller is alright if its warm enough to hang out at the badlands a bit - the museum itself won't occupy enough time.
Maybe a comedy club? It's not unique to Calgary by any means but a nice change of pace from bars/pubs. Yuk yuks at the elbow river casino...and once it's over you can play some poker. If you're lucky Doug Lee will be there playing - he's awful and you can take a few hundred bucks of his money to top off your evening.
