Salon has a good article up on plastic bags, their environmental impact, and whether they're better than paper (the answer is "not really"). The answer, so the article says, is "bring your own," as in buying canvas bags you can reuse for years, and that's a great idea for fixing the t-shirt bag problem. Despite conservative belly-aching, bag taxes in other countries have proven the simplest and most effective way to get people to invest in canvas bags; make the grocery stores charge people even a miniscule fee per bag (around a quarter), and plastic bag use tanks overnight.
Of course, conservative irrationality on pollution and taxes makes this a thornier issue on this side of the Atlantic (and this side of the 49th parallel).
On a different note, the article misses the simple point that t-shirt-style grocery bags are far from the only plastic bags we use, and this solution isn't useful for some of these other bags. How many of you are down with reusable garbage bags?