As your spring garden fades, you can plant some things for fall. Seeds are not as easy to find as they were in the spring, so hopefully you have some fresh seed left over or find some seeds on sale. Here in the upstate of South Carolina you might plant snap beans and beets in early August. In late August consider planting rutabaga, lettuce, and kale. When September comes around there is still time to plant spinach, broccoli, parsnips and radishes. You can plant onion sets and turnips for winter/spring crops. When planting for a fall crop, prepare the soil as you would for a spring planting.
Maybe fall is a busy time for you and gardening is the last thing on your mind. You might consider a cover crop for your garden area. Clover, rye grass, wheat are some of the cover crops you could plant in August. These can be left without much tending and then turned into the soil in late winter or early spring. These will suppress weeds, add nutrients to the soil, and improve soil structure. For more information on cover crops see Clemson cooperative here