Amazon allows to lend Kindle ebooks:

Eligible Kindle ebooks can be loaned once for a period of 14 days. The borrower does not need to own a Kindle - Kindle books can also be read using free Kindle reading applications for PC, Mac, iPad, iPhone, BlackBerry, and Android devices. Not all books are lendable - it is up to the publisher or rights holder to determine which titles are eligible for lending. The lender will not be able to read the book during the loan period.


Finding Lendable eBooks in Kindle Store

Titles in the Kindle Store that are eligible for lending, as determined by the publisher or rights holder, will have a message on the product detail page. Scroll down to the "Product Details" section and look for "Lending: Enabled" as shown below:



For titles you already own, you can check the Your Orders section in Manage Your Kindle. Click the "+" symbol next to a title to reveal additional information about the title. If lending is enabled, you'll see a Loan this book button next to the product image.

See also:
Amazon.com: Lending Kindle Books