This article in today's San Francisco offers some nice solutions to help eliminate one of my big pet peeves: the proliferation of plastic bags. They list a variety of online sources for reusable bags to use for shopping, lunch, etc.
I have a collection of assorted canvas and nylon totes that I use for groceries and other shopping errands, carrying extra items to/from work, extra carrying capacity for travel, etc.
If you've thought about getting some tote bags and just haven't gotten around to it, or the ones you've seen are too expensive, check out the list of vendors at the end of the article. Some of their options are quite affordable, and they come in fun colors and patterns, too.