I get the most compliments from the reusable bags from Home Depot that only cost .99 each!   They clip on to the side of your cart so it stays open and you can just place groceries right into the bags.  I also love the size since it holds quite a bit and they are durable  - would also be great as a beach tote or basically for anything.  They roll up so you can just leave  them in the back of your car so you don't forget to bring them.  They might not be the prettiest looking ones since they are bright orange and have the Home Depot logo on it but it helps the environment with using less plastic.  They are usually found near the checkout counters.