Colorado Springs holds its annual Balloon Classic over the Labor Day Weekend. This is a lot of fun, they have balloon ascensions in the morning and a "balloon glo" after dark in the evening. The "glo" is when all the balloons light up their burners after dark so you can see the balloons all lit up from the inside.
For sheer scenic pleasure, though nothing beats the ascension at first light in the morning from Memorial Park near downtown. The balloons take off and fly off in every different direction.. Worth visiting over a Labor Day weekend some time just to see it!