There's been a gradual move away from mechanically providing customers with physically documented proof that they've engaged in a transaction. Some customer service reps will ask you whether you want a receipt, though if you say no, they just end up balling up the strip of paper their printer spews out and tossing it in the garbage for you. OK, that saves me about a calorie's worth of physical exertion, but it still represents wasted resources for the company, which can really add up over time.
Some businesses have taken it a step further, letting you opt out of having a receipt printed. My bank's ATMs, for example, ask me if I want a printed receipt after a transaction, which I generally don't since I can access that information online. My preferred gas station also asks if I need a receipt, which I don't, because (A) I've never had to return gas, and (B) the purchase will show up on my credit card statement, again which I can access online. Though environmentally friendlier (which translates to less expensive), it's not necessarily a perfect approach in cases you don't think you'll need a receipt but later discover you do (such as when getting a reimbursement from work).
The best approach I've seen, though, is what amounts to digital receipts. Apple Stores, for example, give you the option of having a receipt sent to your e-mail, rather than handing you one on ink-stained processed tree pulp. Thus, the customer has easy-to-find proof of purchase archived in his or her e-mail while -- yes, I'm beating the sustainability drum -- the company saves cash and resources.
A variant here -- another example of technology rendering printed receipts obsolete -- is how some retailers track gift purchases. My wife and I had to return some items we'd received for our recent wedding, but we didn't have receipts. Yet two of the retailers were able to confirm that our items had come from their respective stores (and that one item had not) by checking their digital records. No slips of paper were necessary, and all parties ended up satisfied.
Thus, my second holiday wish to retailers: Retire paper receipts wherever possible, replacing them with more convenient, eco-friendly, inexpensive digital receipts. Paper receipts shouldn't be retired entirely, but at least give us the choice as to whether we need to clutter our pockets, glove compartments, and recycling bins with reminders of last week's burrito or dry cleaning.
Offer greener shipping
My wife and I have a couple of cats, and for the sake of convenience, we order certain supplies in bulk online from Amazon. My thinking has been, "If I buy several cases of canned food at once, it will be more convenient, less expensive, and we'll save on shipping." I'd think the latter point would benefit the retailer as well.