Reusable bags are cool. In particular, I like the ones from ReusableBags.com of the "workhorse" style shopping bag. Laura and I each have a couple, and they're basically with us (in her purse/bag, and in my back pocket) all the time, wherever we go. So, if we somehow randomly happen to need a bag (for shopping or... anything, really), we've got one.
I find them to be strong enough to hold anything I've put in them to date, including some pretty heavy items or sets of items... they fold (or just stuff) down into their attached little pouch quite easily, and once that's done, they're really small. Small enough to fit in... my back pocket, as previously mentioned. Thus, I can always have one with me, rather than the canvas bags I used to use a lot (and still do use for some things), which, while re-usable, you pretty much need to plan to take with you. Which screws you over on the random unexpected shopping trip.
Hence my love for Acme Bags (that's the other name for the same people).
So save the world, and stop using all those plastic bags. (Dog owners, I used to give you an ok on this, but Laura and Sophie have shown me that the cheap small little sandwich bags (which you can get at costco by the... ton?) work just fine, and surely they're lower impact. Hmm, I wonder if you can find those made from corn-plastic. That'd rule.)
Oh yeah, and in my last order, they gave me a little promo thing. You can get a free reusable bag by placing an order on their website that exceeds $25, and putting "FREE ACME BAG" in the comments box. They'll add a bag. (Some limitations apply, but they told me to "pass this offer on", so I feel it's fair game to blog about it.)