Amazon has introduced Kindle Owners' Lending Library http://t.co/wdWsjT7K where Kindle owners can now choose from thousands of books to borrow for free as frequently as a book a month, with no due dates. But the catch is, its only for Amazon Prime members. So in one shot, Amazon is promoting Prime and Kindle. Amazon prime costs $79/year. You can get a Free one month trial from the above link.
How to borrow from Kindle Owners’ Lending Library-
From the Kindle stores, click on See All
Kindle owners Lending Library books will be marked with ‘Prime’ badge
Click on Borrow for Free with Prime.