I live in Evanston and commute to Highland Park when I am not traveling somewhere. I grew up in Madison, Wisconsin.
I have posted several pieces of these routes at
www.gpsies.com, a German site that has an excellent interface for laying out bike routes. Here are some scenarios:
1. Most of the way out to the Elgin area you can ride on city bike lanes or the Illinois Prairie Path. At Elgin, take the Fox River Trail north to McHenry. There, you catch the Grand Illinois Trail (mostly on small roads) west to Freeport. At Freeport, take the Jane Addams trail north to where it becomes the Badger State Trail. The Badger State Trail is almost finished, but has a section that is only single track still. You can shortcut north of Rockford over to the Badger State Trail using minor roads, and shorten this route by about 20 miles.
2. Same as above, only take either the Lake Shore path and the Green Bay Trail or use the Skokie River or Des Plaines River trails to get north to the Lake Bluff or Libertyville areas. From Lake Bluff, there is a marked route west to McHenry. I have this route posted at gpsies.com.
3. An alternative to the Grand Illinois/Jane Addams/Badger State Route (which takes you well to the west of Madison) is what I call the "Hypotenuse Trail." A network of county roads from the Lake Geneva area up to Dane County. I have it charted at
www.gpsies.com.
4. You could always ride to Lake Bluff and continue on minor roads north to Milwaukee, then take the Glacial Drumlin Trail from Waukesha west to Madison. Several minor trails are under construction or already running between Milwaukee and Waukesha, including the Oak Leaf Trail, but I don't know how well marked they are or how direct they are. The Glacial Drumlin Trail costs $4.00 to ride, and has a minor gap near Cottage Grove east of Madison. It's worth it, considering that you don't even need a map, because the Glacial Drumlin Trail is so easy to use.
A good resource would be the Chicagoland Bicycle Federation map, which is for sale at most Chiago bikeshops, and costs about $6.00.
Howard