http://www.the350project.net/home.html In very short: pick three local stores that you want to remain open, spend fifty dollars in these stores.
The site quotes something I've read many times over and a statistic I've repeated in literature for my family's business about how many cents on the dollar (or, in this case, dollars per hundred) that remain in the local economy when the initial income flows through a locally owned business, vs. a nationally owned chain, vs. online. Seems to me this site quotes a somewhat more generous figure than I've seen elsewhere for how much money remains in the community if people are buying at chain stores... that could be owing to a newer study as the big-boxes attempt to capitalize on the public's growing awareness of local economics by planting more charity money down where they've set up shop. Or that could just be Marie cynicism talking. Either way, there are a hundred more reasons to shop local. Yes, you will end up spending a little extra, but trust me when I tell you it's for the right reasons.