Depends what you're into. Some things in the city: Zoo, Telus world of Science, Breweries (tons of micro-breweries that are worth visiting/eating at), going up the Calgary tower (climbing out onto it if you're brave), exploring the river trails, exploring Fish Creek, Stampeder games are a blast too depending on when you're in the city. Just outside of the city there are tons of beautiful hikes or gondola rides (if thats more your speed) in Canmore/Kanaskis/Banff.
Hopefully this helps, just some things off the top of my head