Longer paths

• Des Plaines River Trail (from Wisconsin down to Russel Rd)
  Highly recommended for casual rides. Where else in the suburbs can you ride 40 miles of trail, and very rarely see a road?

  Crushed limestone, with mileposts to boot. Connects many of the forest preserves below. It's wholly within the floodplain, so avoid it when the river level is high. (see stations: Des Plaines, Gurnee, etc)

• Skokie Valley Trail
  The only decent paved path in Lake County. ~8 miles long.

• North Shore Bike Path (east/west)
  West of 43, it's crushed limestone with lots of crapy intersections with high-traffic roads. East of 43, it's paved with bike bridges.

• Robert McClory / Green Bay / et al (north/south)
  TODO: visit here....

Loops

Lake County, IL

• Old School Forest Preserve (east of Libertyville)
  Interwoven dirt loop (2.5mi) and paved road loop (1.5mi). Dirt trail is usually double-width dirt, sometimes crushed limestone. (you can switch between dirt&paved midway, which makes it easier to sprint on dirt and then recover on pavement). The dirt course has particularly enjoyable corners, and the course is possibly short enough that I would enjoy trying to optimize my time around the track. However, as of August 2007, I'm not strong enough to do even a half lap at full pace (I hit max 19mph on the first lap, and took ~15 minutes to go around).

  The corners in the interior dirt section are educational... cornering theory is very useful here. There are also surprises in some of the corners, with some being hard dirt and others loose sand.. so much like road racing, memorizing the course would be very beneficial.

• Independence Grove Forest Preserve (north side of Libertyville)
  Crushed limestone and/or paved. The most picturesque forest preserve in Lake County. It has the Des Plaines trail running down the side. With boat and bicycle rental, it's also a great place to take dates who enjoy the outdoors.

• Grant Woods Forest Preserve (Fox Lake, ~5 miles west of Gurnee)
  Crushed limestone. The south loop is relatively sedate. The north loop has some of the steepest crushed limestone you're likely to find, hitting speeds of 25-30mph multiple times around the ~1.6mi loop. It's ~1.8mi around the south loop, and a ~5 miles for a full circuit around both.

• Greenbelt Forest Preserve (south of Waukegan)
  Crushed limestone. Easy-going place to put miles on the odometer while getting to see other hikers/bikers.

  ~1.8miles around west loop. ~1.7 miles around east loop. ~4.5 miles for a full circuit around both.

• Beulah Park (Zion)
  TODO: visit here... yowzer that looks fun (or at least challenging)

• Half Day Forest Preserve / Wright Woods (Vernon Hills)
  TODO: visit here...

Cook County, IL

• Chipilly Woods (near 94 toll booth)
  TODO: visit here... recommended by someplace that said it might have a little more serious offroad riding

• Mount Trashmore (Schaumburg)
  TODO: visit here.... looks like a challenging offroad trail

• The Bone (Forest Preserve) [1] [2] [3]
  TODO: visit here.... looks like a challenging offroad trail

Wisconsin

• Kettle Moraine (10 miles north of Lake Geneva, Wisconsin)
  TODO: buy a new bike, and visit here... EVERYONE talks about it, allegedly the "best mountain-biking in the midwest".