+1000 to AFrpaso
I'm from the Springs and attend college in Boulder, and he's bang on about both places.
Springs:
Garden of the Gods, Manitou Springs, you can walk around the beautiful Broadmoor, and America the Beautiful Park are my top recommendations. I also highly recommend walking around Palmer Park. Place is gorgeous. Cheyenne Mountain Zoo is always fun. If you're up for the drive, Woodland Park is pretty as well and has great views behind the front range. Eagle's Peak is the famous hike at USAFA and is open to visitors. Moderately strenuous, but well worth it.
I'd recommend eating at the Skirted Heifer in Colorado Springs and O'Malley's Steak Pub up in Palmer Lake. Cadets love it, high school students from Monument love it. Everyone loves O'Malley's, because it's that darn good.
If you're wanting to drive north, definitely hike the Flatirons (Chautauqua Park), tour Pearl Street, and eat on University Hill if you choose to go to Boulder. The college campus is also quite pretty and might be worth a walk-around. Denver has tons of options, I'd suggest 16th Street Mall and Sliceworks.