Well, I find Whispersync for Kindle to be absolutely irreplaceable.

I have a 40 minute drive to work each way, and I find audiobooks the best way to pass the time. At night if I want to read the same book from my drive, Kindle picks up exactly where I stopped listening. And does the reverse the next morning when I get in the car.

If any else is doing this, I am unaware. But it's AWESOME.

My main complaint is Amazon has discontinued Kindle devices with physical page turn buttons. Whoever made that decision should be fired.