Open up the water bottles. Just like your cookware, that tiny amount of water left in a bottle or hydration pack can fester into something evil. Give your water bottles and hydration pack a good cleaning with warm water and a tablespoon of baking soda. Rinse them out with warm water and allow them to air dry. Be sure to store them upside down if possible with the caps open, or loosely attached. A kitchen cabinet is best to make sure they stay clean.
Get rid of the food. Trust us, you won't want to eat that leftover homemade gorp next spring no matter how good it tastes now. Energy bars, powdered goods, and dehydrated foods with the shelf life of uranium naturally can be used next year. Make sure you keep that food safe and away from hungry garage critters. Powdered drink mixes needs to be stored in an airtight container so they don't turn into a solid lump.
Take out the batteries. The flashlight, the GPS, the weather radio, any gadget or device that has a battery in it. Batteries left in electronic devices can corrode and leak destroying them. Some devices continue to slow draw down the batteries rendering them useless in the spring. If you have batteries that are marginal consider throwing them into the recycle bin now.
Store your left over fuel properly. Those fuel bottle half full of kerosene, white gas, or gasoline need a better place to go than your attached garage or in a closet. If you don't have an outside shed you can store them in consider properly disposing your fuel and cleaning the bottle out. Your local fire department can help you with this. Make sure to label the bottles with what is in them if you don't get rid of your fuel. You may not remember which one has the kerosene and which one has the white gas in it next spring.
Get ready for next year now. Fall brings new gear for next year. That also means sales, big ones. If there is a piece of gear you've been thinking about replacing now might be the best time to do it. This is also a good time to buy things like mantles for your lantern that will likely find some way to spontaneous disintegrate while in storage. Replace your consumables now including toilet paper, matches, camp soap, nylon cord and trash bags.