Howdy! Not necessarily alot of caves here, but alot of active cavers!!
If you are near the Corn Desert of Central Illinois, the Near Normal Grotto is fairly active (insert shameless plug here). We have several members that are part of Karst Conservancy of Illinois, the Indiana Karst Conservancy, and not to steal any of Jack's thunder, have participated in Illinois Speleological Survey activities. Mostly we do caving in Southern Illinois and Indiana, but a few of us head to Kentucky to spend time in "The Big One."
In Southern Illinois, Little Egypt holds court, Windy City and Sub-Urban have the Chicago area covered, and Rock River is near Rockford. Pick your poison
Welcome to Illinois and perhaps we'll see you around!
-Troy