Non-U.S. native plants:
Hardy Mums: So many colors available nowadays. Great for fall garden color.

Sedum 'Autumn Joy' (Sedum telephium): Lovely blooms in a subtle pink.

Marigolds: Still in bloom at this time of year for us.

U.S. Native plants:
Asters: Aromatic aster, Heath aster, Smooth aster, etc. Especially nice is Symphyotrichum oblongifolium/Aster oblongifolius 'October Skies', which has very vivid lavender-colored blooms. I have to remember to take a picture of this one to post.

Goldenrod: We have Late goldenrod blooming right now. Some find this plant weedy looking, but it depends on how formal or informal your garden is. It looks great in our wildflower/natural style garden.

I agree that 'Autumn Joy' sedum is a great addition and easy to find.

My marigolds are still putting on quite a show.

Another great plant that has quickly become a favorite (if not THE favorite) is my Acapulco Salmon and Pink Agastache. I LOVE THIS PLANT. It smells like lemon Pledge when you walk by it. Bees love it. I planted mine late last fall. It bloomed non-stop from Spring until...well, it's still HEAVILY blooming. I wish I had an entire garden of them. Seriously. They're marvelous.

An annual that is doing beautifully is 'Strawberry Fields' gomphrena. They look like red cotton balls. They are stunning in bouquets and were easy to start from seed. Seed is very easy to find.

Hosta and heuchera are great for shade gardens. I have many different varieties of those. I've posted quite a few pictures and descriptions on my blog. I'll post the link below. They are great perennials for a spot that gets some shade.

Other info: ('Sprich')- 2’x3’, Z 5-9, full sun-full shade