My love for these just keeps growing. They make great cleaning rags that grab dust rather than spread it around. When one of the resident klutzes knocks over a glass of water, they absorb more than a bunch of paper towels. I put one on the Swiffer I'd had sitting in a closet for ages because I was too cheap to buy refill "cloths". The microfiber worked great!
You can find microfiber cleaning cloths with the brooms and scrub brushes, but you'll get a lot more bang for your buck buying them in the auto department. Target has some great thick orange ones that are super-thirsty for spills. Walmart has a white and blue pack that are smaller and thinner and make great Swiffer or dusting cloths. I find more uses for my microfiber cloths all the time. You can help the environment and save money with these reusable products.
A cautionary note: I love the orange ones from Target, but if you wash them with other things on hot, be prepared to dye the rest of your fabric yellow for many many washes.