One of the easiest ways to be a little more earth-friendly is to bring your own grocery bags. According to The Wall Street Journal, the U.S. goes through 100 billion plastic shopping bags every year - and that is just one country. Worldwide, the number is close to a trillion. Reusable bags are easy - just leave them in your car or by the door - and you will have them handy for the next time you stop by the store. You have probably noticed these reusable bags for sale next to the checkout line at your local grocery store. I have several of these (from Safeway, Top Foods, and Trader Joes). They work great. They hold a ton more than either the plastic or paper bags - and most stores give you a credit of some kind for using them (Trader Joe's enters you into a store raffle for free groceries). If you buy more groceries than me (and you probably do - I only shop for two) it is totally worth it to buy some more sturdy and versatile bags.
My favorite site to find these is resuablebags.com (there is a link in the sidebar). Not only do they have a massive selection of bags for every possible use (they even have reusable produce bags so you can eliminate plastic all together), they have lots of cool facts about the negative impact plastic bags are having on our planet. You can even submit pictures to them of plastic bags you see in your environment.
Like me, however, you probably have some cupboard or drawer full of hundreds of plastic grocery bags that you mean to reuse for trash or wet clothes. However, these bags still end up filling up our landfills. Better yet, clear out your cupboards and take these bags to your local grocery store. Here in the U.S. they almost always have a recycle bin (somewhere near the front door) for the pesky buggers.