After much experimentation, research, and trying out various bags when grocery shopping over the past 3 years, here is the best reusable grocery bag I've found yet:
SteppingStones natural unbleached EcoSac GlobalGrocer cotton canvas bag (http://www.amazon.com/gp/product/B000E8X3J8/).
SteppingStones (http://www.bags4you.com/index.html) is based in Cambria California and this particular bag is currently made in India. SteppingStones seems to be as green a company as you can find in their operations, materials, supply chain, and product design. See http://www.bags4you.com/company/company.html
What I like best about the GlobalGrocer:
- very sturdy (can hold very heavy groceries or serve as a book bag even -- they are very versatile)
- great handles -- not too short, not too long, and wide enough to hold easily
- can sling handles over your shoulder or hold in your hand
- folds flat
- quite large so holds a lot (but not too large) 18" x 16" x 7"
- very tear resistant
- since they are not mesh they can contain and absorb liquid and dry leaks and spills
- made of a naturally sustainable, reusable, and recyclable material (cotton)
Some alternatives I've tried but don't like as much:
Woven polyethylene bags
- These are the most common reusable bags around and generally fold flat. They are lighter and stand up a bit more on their own when loading but are not as strong and they are torn relatively easily by simple things like the corner of a kleenex or cereal box.
String mesh bags
- Lighter but they snag, don't contain spills, and small items fall thru some mesh variations.
- Many other bags of various materials just haven't been the right size or shape to hold groceries effectively or don't fold flat or into some other convenient shape for storage. We do have a couple of recycled plastic reusable bags we bought at Whole Foods that are very sturdy too but I don't like them as much as the cotton Global Grocer.
We keep a set of 6-8 bags in the trunk of each car we use to shop. That way we don't leave them behind. We also keep a set of clean reusable plastic food containers in our car so we can put restaurant leftovers in them rather than using disposable take out containers.