Apparently, you can loan some Kindle books now:
From an Amazon Help page:
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.
And there are directions on that page for doing this. Anyone feel like testing this feature and giving us a trip report?
Edit: Okay, I found a couple books that had the "Loan This Book" button, and it looks like anything that can be loaned will use the Nook model. I.e. lend it once for 14 days, and that's it. This included a book that I know that the author published on his own through Amazon, which makes me think that the feature is more or less an item they're putting in so that Barnes and Noble can't say they're the only ones that do it.
I do wonder if self-publishers will eventually be able to make it so their book can be loaned more than once, but I also doubt that Amazon has made provisions for that straight off.