I have very strong feelings about plastic shopping bags. Over three years ago, I sewed my own bags. I love them. I refer to them as my "Mary Poppins bags" since you can fit TONS of stuff in them.
I used the Kwik Sew Pattern 2191 and marked down indoor/outdoor upholstery fabric. The great thing about using this type of fabric is that it is incredibly sturdy and stain resistant. Of course, my husband likes to point out that my bags look like they came from an old woman's couch. Eh, I don't care. It was a low cost investment in a high use product. Seems like a win/win to me.
As you can see, the bag is virtually identical in size and shape to a traditional paper grocery bag. The pattern is perfect for someone new to sewing also. The bag is cut as one piece and sewn with four straight seams (which are subsequently reinforced). There is a simple fold down hem on the top.
I have made several sets as gifts for friends. Everyone has enjoyed them and all bags are still totally functional and in great shape. I throw them in the wash and hang to dry. I have had a gallon of milk, two 2L drinks and a 2L juice in one bag. It was heavy, but easily withheld the weight. There was still room for other items on top of the bottles!
Since I had shopping bags down pat, I became more annoyed with plastic produce bags. I came across these. They work wonderfully. I even store the fruit/veggie/herbs in the frig while still in the bags. I toss them in the wash and hang them to dry. I have not had any problems using them at stores.
I fold all the bags and store them in a shopping tote in the back of my car so they are always handy.