You've probably already caught up with the announcements by Overdrive and Amazon that they are collaborating on a Kindle ebook lending service.
The details are not very clear at the moment but it seems to me that it is simply an extension of Amazon's existing Kindle ebook lending service which allows those in the US who've bought Kindle e-books to lend them once. While the book is lent (for two weeks) the purchaser can't access it on their Kindle. The book can only be lent once, and it doesn't necessarily apply to all purchases - publishers need to give permission.
Crunch Gear has basically republished the media release word for word.
Not much joy here for non-US Kindle users though. Of course Amazon's Kindle e-book lending does not extend outside the US at the moment, so perhaps in the future...