By clanders in November, 2010
Salt Creek Trail in the Bemis Woods Forest Preserve - wooded forest preserve paved path in good condition, but subject to flooding during heavy rains, especially in the spring. From the trailhead at Mc Cormick Ave & 31st street (just west of the zoo's north parking/entry), there are five major road crossings of busy roads only one of which is at an intersection with crossing lights, however, the others are well marked. This trail is heavily used by bikers, runners, and walkers.
The original 6.6 miles from the Brookfield Zoo to the western edge of Bemis Woods Forest Preserve has been extended to a 32 mile route that ends at the Busse Woods trail loop. The project is officially complete and it is possible to ride from the zoo to Busse Woods. The 0-mile is at the intersection with the Busse loop south to the 32 mile marker near the zoo. There are some on street sections along this route, but most is paved trail and some crushed limestone trail.
More info here:
http://www.1track.org/SCGT_w.html
http://geognerd.wordpress.com/2010/07/03/salt-creek-greenway-trail/
http://www.elmhurstbicycling.org/advocacy/pdf/map-6.pdf