Feather Falls has to be one of the best waterfalls in California (outside of Yosemite), especially in the spring.! It's located in Plumas National Forest and can be visited year-round. The hike is 7 to 9 miles depending on which trail you choose to take. There is an elevation loss of about 1000 feet on the way to the falls.
There is no entry fee.
For more details check out the Feather Falls Norcalhiker blog post.