Hi, Julie,
Fall is one of our favorite times of the year, too! Couple of things to check out:

1. The Color Report from the Arboretum’s Color Scout Ed Hedborn updated at least weekly:
http://www.mortonarb.org/whats-in-bloom/weekly-color-report.html

2. Fall activities and events in the calendar section of SEASONS magazine (if you are a member) and online at the Calendar tab:
http://www.mortonarb.org/calendar/article/15527/fall-color-festival.html