New Twist on an Old Thing

One of my favorite things about my new home in Little Rock is its proximity to a place called Rivermarket Books. I didn't realize exactly what it was until I put my $12 book on the counter and they charged me $4 for it. After I got over my shock, they explained that the store is stocked almost exclusively by donated books. Most of the books are used, but there is decent selection of vendor-donated, new books too; therefore, they can charge really low prices.
I was familiar with Half Price Books in San Antonio. I like Half Price Books, but I've always been disappointed by the amount they pay for a used book in comparison to how much they charge for it once it's on the shelves. They pay practically nothing for most books and charge significantly more than Rivermarket books. I'd much rather give my books to Rivermarket Books for nothing and pay less for the books I find in the store. I'm curious about other areas in which this business model might be successful.
I've asked myself the same question about Tom's shoes. Their one-for-one business model in which every pair of shoes bought results in a pair of shoes being donated to someone in need intrigues me. The business seems to be successful and helpful, which makes me wonder if the same model could be applied to other goods: other clothing items, computers, food...