Blog Kindle has a step by step article on this today:
So, you’ve written a book? Congratulations. Whether it’s the work of years or simply your latest NaNoWriMo entry, it was almost certainly a difficult and demanding project that it would be great to get some recognition for. Sure, you can go through the traditional routes and send out your manuscript to the publishing houses in hopes that you get a bite, but should you be looking for another route, whether due to rejection, disinterest, or simple distaste for involving yourself with those companies, Amazon’s DTP(Digital Publishing Platform) for the Kindle might be right for you. Here’s how it works
Kindle/Amazon has been the best for customer service so far. Our company uploads books for corporate accounts and they have a great training for us and communication. Unlink some of the others. Apple/iTunes is the worst and just received a message from them yesterday in their back office that the Apple iProducer program will be down November 23-December 22. Just in time for all authors wanting to get their books on the iBookstore before the holiday rush.