Amazon has announced a new program of lending its Kindle books. Following Barnes & Noble's lead with its Nook e-book reader, Amazon now lets users "lend" books for 14 days to others even without a Kindle. While the book is on loan the original owner can't read the book.
Not all books are available for lending. Publishers and authors need to authorize such use. Books which are available are noted as being Lending: Enabled in the product details.
Remember: if you order from Amazon from the library's website the library gets a small percentage of the total.