the 19 stop Hellmuth Wolff (Op. 37) at St. Giles Episcopal Church, Northbrook, IL ; The 23 stop Lynn Dobson organ (Op. 81) at Kenilworth Union Church, Kenilworth, IL and the 27 stop Martin Pasi organ (Op. 15) at the Episcopal Church of St. Paul, and the Redeemer, located near the University of Chicago. Here is a link to the Kenilworth organ on Dobson' site, showing how the organ itself was built. Here (below) is a picture of the interesting embossed pipes on the Dobson.
Below is a picture of the Pasi in St Paul and the Redeemer. I really like the ribbons over the altar, too.
Below is a picture of the Wolff at St Giles' Church, Northbrook and here is a link to the Wolff website for the specs and other information.
What are trackers, anyway? Well, right above this is a picture of the insides of a tracker instrument and you can read one church's explanation of how organs work here I suspect that I'll be editing this soon with some input from John Speller on websites that explain how organs work.