Snowshoeing is gaining popularity and allows access to all the following places without the need for skiing ability. Sugar Pine Point State Park offers approximately 20 kilometers of cross-country trails, 10k of which are groomed. Beginners love the blue trail - it's very flat and well maintained. The red trail is a bit more challenging, climbing westward, crossing General Creek, and returning via an easy descent through Olympic Meadows. Two other trails, on the Ehrman Mansion side of Sugar Pine Point State Park, afford great lakeside skiing, but depend on skiers to break trail since there is no grooming on that side.
Winter camping is also available.
Blackwood Canyon is the easiest of these. It's the most accessible, being part of the California Sno-Park program. The trail at Blackwood Canyon is actually a snowed-over 2 lane road that ascends very gently 2.5 miles to the bridge across Blackwood Creek. This is the place to in-line skate during the summer season. From the creek, the road climbs to Barker Pass, another 4.5 miles, with a pretty rigorous climb.