It's one of the strangest corporate hookups I've seen lately, but I can't deny that it makes sense. Today Motley Fool Hidden Gems pick Coinstar International (NASDAQ:CSTR) and Motley Fool Stock Advisor pick (NASDAQ:AMZN) announced a partnership that will allow consumers to drop their loose change into Coinstar's machines and emerge with a gift certificate good for buying anything Amazon sells, from a new Apple (NASDAQ:AAPL) iPod to doggy pee-pee pads. (Seriously, my colleague buys these from the 'zon.)

The good news for coin-hoarders out there is that the gift-card option frees you of the usual 8.9% fee.

Of course, Amazon isn't the only company getting in on this action. The fee-less gift-card deal is also available from Starbucks (NASDAQ:SBUX), Movie Gallery's (NASDAQ:MOVI) Hollywood Video, and Pier 1 (NYSE:PIR). To be fair, I think this kind of system synergy makes more sense for Starbucks and Movie Gallery, since it's easier to imagine people coming up with $10-$20 in coffee money than a couple hundred bucks for a wicker armchair or a digital camera.

It's difficult to judge whether there's any quantifiable takeaway for investors in these deals. Obviously, Coinstar must be getting some kind of kickback for putting together these programs, but we don't know what it is right now. And Starbucks, Amazon, et al. obviously see some value in getting a shot at money that would otherwise be hiding under the couch cushions. Presumably, they're willing to pay something for that.

Perhaps the investment lesson here is to keep your eyes open for the myriad ways that companies can redefine the mechanics of payment services and benefit through fees and float. Like eBay's (NASDAQ:EBAY) Paypal, Coinstar can not only collect percentages for services, but also, with gift cards and other pre-paid products, it can collect money up front and pay it out later (with the opportunity to invest it in between.)

So, people pay you (or at least charge you nothing) for the privilege of loaning you their money at 0% interest, and you can do what you want with it until they collect? In the business world, there aren't many deals sweeter than that.

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Seth Jayson prefers to dump his change into the free machine at his local bank. At the time of publication, he had positions in no company mentioned here. View his stock holdings and Fool profile here. Fool rules are here.