I've become a huge devotee of reusable shopping bags, especially for groceries. I have about 10 that I keep in my car at all times, so they are always ready to go in to the store with me. They only cost about 99 cents, and most grocery stores give a bag credit for using them. You would have to use the bags a long time to recoup the costs, but that's not why I use them. They are stronger than either paper or plastic, hold more groceries, and don't clog up the landfill when you are done with them. I've washed them when they've gotten stained or dirty and my mother-in-law has sewn up the side seams when they've split. I think it was Fred Meyer that was advertising that you could save 400-600 bags per year just by using 3 reusable shopping bags. What's not to love about that?
I have always reused my plastic grocery bags as trash bags throughout the house (even in the kitchen, where our trash can is under the sink), so I was afraid that I might run out of my supply at some point. That hasn't yet been a problem, and I've been using the reusable bags for at least 6 months now. Every now and then we will find ourselves in a store without a reusable bag, and whenever we are at Target, I always get their bags because they are thick and easily the best quality bag out there--perfect for kitchen trash!
I have a really cool reusable bag that I got from Dress Barn (Target also carries them) that collapses and snaps into a very compact, easy-to-carry square. I keep it in the passenger door of the Sienna so I can pop it in my purse when I am heading into a store for some non-grocery shopping.
If you haven't started using reusable bags, I challenge you to get a few this week and give them a try. Your landfill will thank you!