Need to kneel in your garden to pull weeds, or on the street to change a tire, but don't want to preserve the memory eternally on your pant legs? Grab a couple of plastic bags and tie one around each knee, covering the area that will be exposed to dirt and grime.
For no-fuss cleanup, instead of peeling fruits and vegetables over a cutting board or into the sink, do it over a plastic bag. When you're done, flip the peelings into the garbage and rinse the bag to reuse another day, or simply toss the whole shebang into the trash.
Crumple bags to fill the bottom of a large pot that's too deep for your plant (but be sure not to cover the drainage hole, if it has one). You can cut down on the amount of potting soil needed, and since plastic packs less heft than dirt, you'll be able to move a big planter around with a bit less grunting.
To avoid dripping water all over your (or anyone else's) house on a rainy day, pop your wet umbrella into a bag as you cross the threshold. You can even tie the handles snugly and throw it back into your purse―unless, of course, your bumbershoot is of Mary Poppins proportions but your carpetbag isn't.