Every year, travellers worldwide throw away about $10 billion in pre-paid hotel bookings, and $7 billion in unused flights. Thankfully, in the past 12 months, three secondary market websites – similar to CraigslisteBayand StubHub — have debuted services that take some of the risk out of purchasing.

Selling unused flights and hotels is new – and a tad trickier. Because few people know about these young sites, they can sometimes feel like empty street markets. They’ve yet to attract a large number of buyers and sellers, a dynamic that can be self-perpetuating. It’s best to think of them as outlet stores for vacations and to dip into them for occasional bargain finds.