If you're like most people, you deal with a bunch of them: grocery bags, bread sacks, bags the newspaper comes in when it's wet out and so on. Most of us don't throw them out. Some return them to be recycled and some recycle them right at home. I used to have pages full of ways to save them on the About site. There really are that many ways to use them.
Basically, though, there are only a handful of reuses: As waterproof containers, as raw material for crafts, as protective covering and as utilitarian material.
Waterproof containers can carry wet clothing or keep items dry in wet weather.
Raw material for crafts include cutting strips and braiding into door or shower mats, knitting or crocheting into any number of useful and beautiful items.
As protective coverings, slit a bread sack down one side and put it over a bowl bound for the refrigerator. Twist the end and slip it under the bowl for an air tight cover. Or tie grocery sacks around your knees before kneeling on wet or muddy ground (to change a tire or garden).
Make a utility rope from plastic bags by fastening them together like rubber bands, slipping the bag only part way through the hole made by the handles of another bag, then pulling tight. The strength is amazing.
That's hardly the tip of the iceberg, but I hardly ever have any to dispose of.