Hike the incline, climb in Garden of the Gods, bike at Rampart Range. If those things don't interest you, then visit Manitou Springs-a funky town. There are several plane crash sites in Pikes Peak National Forest. Grab your GPS and explore them-especially the B25 bomber near the Academy. Geo-caching is really fun too. Try white-water rafting or skydiving-I jumped at Centennial airport.
Exhausting all the options in the mountains is next to impossible. There's spelunking, hunting, fishing, boating, canoeing, white water rafting, snowboarding/skiing, mountain biking, ATVing, etc.