Amazon has just announced Kindle Library Lending – a new feature that allows Kindle users to borrow e-books from over 11,000 libraries in the U.S.

Kindle owners and users of the free smart phone app – which is currently available for iOS, BlackBerry OS, Android, and Windows Phone 7 – will be able to take advantage of Kindle Library Lending. And what’s more, Amazon is improving its Whispersync technology to make annotating borrowed e-books possible. As outlined in a press release, which hit the Web earlier today:

“We’re doing a little something extra here,” Marine [Jay Marine, Director, Amazon Kindle] continued. “Normally, making margin notes in library books is a big no-no. But we’re extending our Whispersync technology so that you can highlight and add margin notes to Kindle books you check out from your local library. Your notes will not show up when the next patron checks out the book. But if you check out the book again, or subsequently buy it, your notes will be there just as you left them, perfectly Whispersynced.”

However, Apple’s new in app policy – which must be supported by all iOS apps by June 30 – has left many wondering exactly how long the universal Kindle iOS application will remain in the App Store. If Amazon doesn’t offer an in app method of payment before this date, Apple may remove the application from the App Store.

Currently, Kindle is available to download in the App Store for free. Check out the new feature, and let us know your thoughts in the comments.