A fellow PSAWSLD (*Price Sensitive Affluent/Wealthier Shopper Who Likes Deals) has pointed out an amazing one: upgrading to Amazon's Prime Shopper status. It seems that for $79 annually, you receive free 2nd day shopping on ANY Amazon purchase, and for $3.99, you can upgrade to Overnight Shipping. And amazingly, you can enroll up to three other members of your household in this deal. Once you set them up on your account, their shipments don't have to go to your house. Clearly this is more of a buying group than a family - they specifically mention that your household members will need to know your birthday to sign on through your account. Most family members know one another's birthdays, I'd say!
Obviously if you buy a lot of books, this pays for itself after the 20th book or so, but Amazon has expanded into every area imaginable. My friends use it for all sorts of household purchases, in addition to their academic lit purchases . It's also a time-saver, since it is fairly common to find an item on the net and discover the shipping exceeds the cost of the item, or just in general a rip-off amount. If you're like me, and stubborn about these things, this results in restarting the search. And it's an anti-Schwartzing technique, too: it eliminates a whole lot of options - you just go with what Amazon has to offer, and it's probably fine. ("Schwartzing" is named for Barry Schwartz, the Swarthmore professor who has written The Paradox of Choice - showing that when we have too many choices, it is anxiety provoking and actually decreases our happiness.)
It's hard to know how Amazon can make money with this arrangement, but apparently customers are loyal, once they have plunked down $79.
In my experience, once you pay the charge, you never think about it again, and enjoy the free shipping each and every time. (Of course it's only free after your 20th purchase, but it's not hard to imagine purchasing 20 items through Amazon in a year.)
Epilogue: I joined Amazon Prime for a trial month (free) and the first two purchases I attempted were not covered under their Amazon Prime policy. Apparently books generally are, but for other product, each vendor that subcontracts with them has its own policy. Caveat emptor!