Planter Fillers
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.
Knee Pads
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 entire area that will be exposed to dirt and grime.
Hand Protectors
Fact: There are some things you'd just as soon not touch with your bare hands. Use bags as gloves to handle what's messy (say, chicken carcasses) or just plain gross (like the little "presents" the dog leaves in the front yard), then turn them inside out to trap the offending matter inside for easy disposal.
Paint Preservers
You're painting the kitchen when an emergency (kid's sick at school; Brad Pitt is Ellen's special guest) calls you off the job. To keep brushes and rollers from drying out, place them in bags and tie them or wrap them with rubber bands to keep air out. The tools will stay moist and protected for a day or so.
Makeshift Rain Hats
A 30 percent chance of rain…hmm. Do you tote around an umbrella (maybe for nothing) or head out sans protection (and risk getting drenched)? Third option: Tuck a plastic bag into your pocket or purse. Then, if you're caught in a downpour, you can use it as a makeshift rain hat to protect your do.