Keep child-size brooms, dust pans and other cleaning supplies on hand. Encourage children not just to help you when you sweep up, but to sweep up their own messes whenever they like. Store these items in an accessible place so they can get them out when they like. My son loved to clean windows when he was little. We used a solution of nontoxic vinegar and water in a small spray bottle instead of chemical-laden glass cleaner. He had fun, was safe, and I didn't have fingerprints all over the lower three feet of my windows.
Step stools are a must. Children like to help in the kitchen, even with the mundane chores. If you are doing dishes, a step stool allows little hands to help and learn. The same goes for cooking and other food preparation activities.
I even advise involving young children in home repairs when feasible. We keep a toolbox of child-size tools handy. Even if the project is too involved or dangerous for the child, he can sit nearby with his tools and hammer nails into scrap wood. He is learning the joy of work, even if he isn't directly helping.