Check & clean your dryer vents. This one is more serious than it sounds – excess lint buildup can dramatically increase the risk of fire. If you have a flexible dryer duct in poor condition, consider replacing it with a rigid duct.
Start storing (or covering) your outdoor furniture, grills, hoses, flower pots, etc. to protect them from fading or winter damage. Once you are done using your external spigots for the year, shut off the water supply to each & open the faucets to drain the remaining water. This will prevent damage from freezing.
Seed bare & damaged spots in your lawn. The drought we experienced this summer might mean your lawn needs extra TLC this fall, and seeding before the first frost of the season is proven to be a very effective way to get a jump on spring growth.