This is a very basic route to the summit of Niwot Mountain. It is Class 2 and uses an old mine road to come within several hundred feet of treeline. In wintertime, this old road remains fairly well windblown, allowing for a ski or snowshoe approach in winter, though avoiding for the most part the postholing I've heard associated with the straight North Slope Route.
Drive to the winter closure of Brainard Lake Road, where Left Hand Reservoir Road branches from the main road to the left. See directions for how to access the Brainard Lake area on the main mountain page. To approach this route, hike, snowshoe, or ski up the Left Hand Reservoir Road, depending on your preference, to near the point where the Little Raven Trail (not the Little Raven Extension Trail) branches right from the road. Opposite this trailhead, on the left of the reservoir road, you will see an open, rocky, treeless section of land that apparently was an old mine at some point. The route begins here.
From the Left Hand Reservoir Road, facing south, enter the old mine area, keeping west. Your goal is to hike (or ski or snowshoe if it is wintertime and this area has not been blown clear by the pervasive winds) to the highest clear point on the west side of the mine site. In plainer English, you want to hike as high into the clear area as you can, keeping right. In this right high corner there is the beginning of an old road. You will know it is the old road by the broken tree laying in its mouth near a Forest Service marker declaring the obvious clear trail a closed road (all noted in Jan. and Feb. 2008).
This road will take you at a seemingly backwards angle of approximately 130 degrees, slightly away from the mountaintop you are seeking. Do not worry. Keeping on this angle you will follow the old road for a short while until it terminates near treeline.
From the end of the old mine road, if you turn to 210 degrees, the summit of Niwot Mountain will be obvious and the views back to the north will be spectacular. If you have not already stashed or strapped to your back your skis or snowshoes, now would be the time to do so. Punch through the sparse trees on this shoulder of the mountain and follow the high ground at roughly 210 degrees to the summit. From the summit you can ramble Niwot Ridge, find an alternate route down to Left Hand Reservoir to the northwest, or simply return the way you came. If you retrace your steps, be sure not to dive into the trees to the right of where the old mine road terminates, or you might walk too far down the hill. In any case, an offset to the north of the route you ascended will land you on the old mine road or at least lead you to the Left Hand Reservoir Road at some point.
Basic hiking, skiing, or snowshoeing kit, depending on the season and your preferences. Be aware that the winds in this section of the world have the potential to be terrific, if not brutal. As usual, be aware of general weather-related Rocky Mountain hazards.
Thanks to Greenhouseguy from 14ers.com who turned me on to this easy, posthole-free winter route. His illustrated TR from winter 2007-08 is here