This idea isn't nearly as creative as some of the others on this board already, but sometimes the simplest ideas turn out to be the best
I present to you, the T-shirt Shopping bag:
You can make this 100% out of materials ANYBODY has, and with a sewing machine you can make one in about five minutes. Basically, use the bottom hem of the T-shirt as the top edge of the bag, and then cut horizontally across the shirt as deep as you'd like. Use the excess fabric from the sleeves and shoulders as a strap, and the collar is cut to form the ties. I boxed the bottom, but it isn't really necessary.
(Moderately full of random things from my apartment
T-shirt fabric is generally super stretchy, but it retains its shape when not fully stretched. Thus, it is the perfect grocery bag, because you can carry a little or a lot with one amazing bag! As an added bonus, you won't need to take a million bags if you make one or two of these. I live alone so I fit 95% of my purchases in this one bag.
If you were wondering, I HATE carrying things around in my hands if not necessary (this is what bags are for!) which is why I made a shoulder strap. I think it would be just as easy to make handles if that is what you prefer. To solve the problem of the strap stretching along with the rest of the bag, I simply lined it with a non-stretchy fabric I had around.
With a bag this easy, there's no excuse not to be GREEN!
(If anyone else has thought of this before, great minds think alike <3 - I didn't see anything similar when I searched, so I just had to share!)