Outside Magazine just (re)featured an article about the sometimes-secret gems that are state parks. National Parks get all the glory, and rightfully so--they're generally the most awe-inspiring places in the nation--but there's a lot of other good land, too.
To get to the summit of Sheep Mountain on the Round Mountain Recreational Trail, you take the "Summit Adventure" route. The trailhead and parking lot are 4 miles west of the Dam Store in Loveland, Colorado--on US 34 along the Big Thompson River.
The first mile of the trek offers views of the Big Thompson and US 34, which are pretty cool considering the completion of the new road. Then you switchback farther into the wilderness, and things quiet down. I like hikes like this because the payoff of the uphill is just being able to see farther and farther. You'll come to a split rock, and a spring, and mile markers, but the reward is just being present: seeing Rocky Mountain in the distance.
Buy your pass to the national parks for sure; but also, soak up what's just down the road and maybe not as popular.