If you happen to be in Wisconsin, be sure to rent a bike and check out the John Muir trail in the southern Kettle Moriane area. You can rent a bike a the LaGrange general store on highway 12 and county H. Rates were ~$40 per day for a full suspension, but you won't need that much bike, this is definitely a hardtail or singlespeed type of trail. The general store is ~1.5 miles from the trailhead and you can get food/beer there before or after your ride.
Let's face it, it's not the most technical trail in the world, but if you're looking for some fast singletrack and some variety, it's the best that you'll find in the area.
Location: Palmyra, WI
Directions: Take Highway 12 the the intersection of 12 and County H. From there go east about 1.5 miles to the park entrance. There is a large parking lot there.
Technical Level: Low