I carry a ChicoBag with me everywhere I go. Because they compress to such a small size, I keep one clipped to my keyring so I never forget to take it with me. They say the bags hold 20 lbs, but they definitely hold more, as I've stuffed mine with books to return to the library and tons of other items. Unlike regular tote bags, these bags are designed to be the same size as the shopping bags we're used to.
According to Ed Begley, Jr., "ChicoBags are the perfect way to cut down on the wasteful use of paper and plastic. What makes them better than many other bags is their compact nature. Now, there's no longer any excuse for not having a bag with you!"
The bags come in a variety of colors, can be used for stocking stuffers, gifts (I've given them to friends who love them), and are machine washable. I also like that you can send them back to the company if and when they wear out and they'll recycle them into welcome mats, pet beds, prayer flags, etc.
Oh yeah, and check out their Bag Monster videos on YouTube and on their website. Funny stuff!