University Of Illinois Extension has done an excellent job of posting page after page of helpful gardening resources.  You can find a step by step planting guide, tips on growing specific vegetables, and suggestions for insect and disease control here: University of Illinois Extension, Illinois Vegetable Garden Guide

Small Farm Educator, Bill Davison has come up with a month by month garden schedule that includes a weekly breakdown.  You can find his guide here: University of Illinois Extension Serving Livingston, McLean, and Woodford Counties