Lately, we we've settled on a real winner. This is the market bag we reach for and are determined to use regularly: the MiniMaxi Shopper from Reisenthel ($4.99 on eBay).
These handy polyester bags comes tucked into a small storage case that's just four inches by two inches. When unfurled, these bags hold a large amount of Greenmarket produce plus whatever else we're toting around town, without looking bulky from the outside. They come in more than 20 different colors and pattern variations.
We appreciate the light weight, but realize that some people will prefer bags made of organic cotton and other greener fabrics. As Whole Foods and other grocery stores stop giving out plastic bag and cities move to outlaw plastic bags, we'll be hearing more about re-usable bags like this.