Downieville Downhill - The Downieville Downhill is a combination of 4 wheel drive trails, fireroads, and singletrack that stretches 19 miles from Packer Saddle to the town of Downieville. There are multiple ways down but all of them are incredibly fun. It doesn't get much better than this.
Downieville Big Boulder Trail - Like the rest of Downieville but skinnier, trickier and more fun.
South Yuba - A phenominal cross country ride about 45 minutes north of Auburn. Awesome views, fast hairy buffed singletrack which makes you drool. A local favorite in the winter when the snow closes the higher trails.