Just now Amazon quietly launched the Kindle for Mac.
The new applicaiton is a very basic that fucntions exactly what you expects a Kindle application on the Mac does. It downloads your purchased Kindle books from Amazon, so you can read them on your Mac. The application also use Whispersync to synchronize the spot in the book where you left off when you last read the book. The functionality is not that much different than the Kindle for iPhone app. The only major addition is the Mac version’s ability to resize the screen displaying the book.