I just got word over twitter that Amazon have enable ebook lending for the Kindle. Here's the summary from the help page, and you can find out ore from Amazon.
Eligible Kindle books 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 our 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.