Plastic bags that have been used once before can still be used to carry clothes; dirty or clean. Wet clothes are quite well insulated if two or more plastic bags are used. Sports shoes can also be kept in plastic bags.
Plastic bags are especially useful for padding; using them to cover your knees, hands and feet allow you to do the dirty jobs without having to come in contact with the mess. For example, gardening, walking through muddy areas and cleaning up after your pet are all tasks that leave stains on clothes and make you come in contact with unpleasant substances. Plastic bags act as a barrier between you and these things, and you can just throw them away after you're done.
Use plastic bags to hold your rubbish at home! Keeping rubbish in a plastic bags makes transportation to the bin much easier, and gives you a place to put your trash and scraps.