"Fall gardens don't happen without summer planning!" - Me, I said this ;)
Use this guide to determine your first frost date, remaining frost free days and to get some ideas of things you can plant in the summer for a fall harvest!
So many people only think to plant in the spring when all the stores have thier seedlings for sale. Yet in some cases this isn't even the best time to plant certian varieties! Some plant (ie: brassicas) taste better after they have been touched by frost!