Arm & Hammer Air Filters, 4-Packs | $20 | Home Depot

You all know this, but replacing your air filters is one of the cheapest ways to improve the air quality in your home. They can remove funky smells and allergens and, especially important this time of year, make your AC unit more efficient. Home Depot is selling a whole bunch of 4-packs of Arm & Hammer air filters for just $20 today. So go ahead and stock up.