San Jose has banned plastic shopping bags, and more and more cities are following suit. While there are plenty of inexpensive bags available, it's fun to sew some bags that are unique and functional. In addition to shopping bags, there are patterns for lots of other bags to fill lots of different functions.
Simply Sublime Bags features some really cute bags, including one made from an old t-shirt, reinforced with duct tape to give it some structure. The author makes use of other materials, such as pillow cases and placemats, to make quick, easy bags, as well as using staples and duct tape for no-sew bags.
Sew What! Bags has three different tote bags in different sizes, some flat, one with sides, and with pocket options, with encouragement to modify them to be perfect for you. There are also drawstring sacks and messenger bags--plenty of options for carrying different things!
You might not want to use Lunch Bags! to make shopping bags (although some of them are large enough to work), but there are lots of cute alternatives to brown bags. In addition, if you're trying to reduce your use of other kinds of plastic, instructions are given for sandwich bags and snack bags.
The easiest bag of all comes from the Japanese. Furoshiki Fabric Wraps (foo-roe-shkee) are squares of fabric knotted together at the corners. While used for gift-wrapping, the same idea works to create an easy bag.