There are two kinds of radishes that can still be planted. In late summer try seeding winter radish. Later for early fall it would be time to seed the spring radishes. Another root crop to consider is turnip. Turnips are very good when they are not too big.
Out in the perennial beds, gardeners could be dead heading the flowers to prevent volunteers coming from seed in places you don't want them next year. Deadheading can turn that bed back into something that looks a lot better when what is left is the foliage without out all the brown flower parts. Planting of mums is done now if the goal is to have them established before the cold weather for permanent plants in the bed. Lots of perennials are divided and re-set in the late summer.
It is still too early to dig and lift the summer bulbs, but not too early to plan where those spring bulbs will be going if a new planting is to be done. Daffodils will multiply on their own while tulips never seem to. If your daffodil plantings have been more foliage than flowers, then it is time to dig and divide them any time now. While they are dug up there is also the opportunity to clear the bed of weeds before resetting the bulbs. Before you reset the bulbs, incorporate some organic matter into the backfill soil to provide better drainage and provide nutrition throughout the root zone. To get the bulbs settled in the new planting, water them in well.
Late summer and fall are great times to replace shrubs and trees in the landscape beds and foundation plantings around the home. A wide variety grown in containers and balled and burlapped plants are available. Plant no deeper than the soil in the container or the top of the balled and burlapped plant to ensure the root system is not too deep in the soil. Go one step further with container plants and be sure to really rough up the root ball with your hands or a garden knife if needed to re orient the roots so the grow out into the soil as transplant recovery occurs. Water the plants well at the time of planting and continue to water well into the fall and one last time just before you put the hose away for the winter. If gardeners take care of new plantings through late fall, then the rewards will be seen next spring.