Most grocery stores around the country are selling some sort of reusable bag. Of course, you can collect reusable bags just about anywhere these days. 
A super idea that Stop & Shop came up with was to give you 5 cents for every reusable bag that you bring to the store to use on your shopping trip. From my wife's experence, it doesn't matter if they say "Stop & Shop" on them. Here is more information on this program and other things that Stop & Shop is doing to help in this effort:
One of the national chains that helps a lot is Home Depot. Here are some great links on their website for "Going Green":
Home Depot offers a list of products eligible for tax credits under the "Tax Credit Eligible Products" heading
Home Depot also offers environmentally friendly tips and product recommendations here
I know how overwhelming all of this information can become as I did a great deal of this research while getting my Realtor GREEN designation, so I will give it to you in "short" blogs. Would anyone else like to share information about how stores are getting on the Green Bandwagon?
Chris K. Canfield
REALTOR®, ABR, CRS, e-PRO, GREEN, MRP, SRES
Coldwell Banker Residential Brokerage
2890 E. Skyline Drive, #250
Tucson, Arizona 85718
Our local store encourages you to bring back all plastic bags, and buy re-useable bags at the store.
I try to make sure I have my reusable bags in my car for impromptu trips to the grocery store, if purchasing small items at Target, will forgo the bag all together.
As you can see from the photo, we collect reusable bags. This way we can have a stash in either car, and when the kids are out and we need them to make a quick stop at the grocery store, they can't use "but I don't have the reusable bags with me" as an excuse. (They will just find another excuse.) : )