Check out Park City, a mountain town with three major ski resorts that keep on rocking in the summer months. Highlights include ziplining, mountain biking, hiking, hot-air balloon rides and summer concert series. For something a little more luxe, check out Sundance, about an hour south of SLC. Robert Redford's brainchild, Sundance has a full slate of outdoor adventures (including mountain biking, horseback riding, and fly-fishing) and environmental programs, not to mention a full-service spa.