Publishing Your Ebook
There are absolutely no fees for creating an author account and uploading your book to any of these sites. If and when your book sells, they will send you the commission either by check or direct deposit. You never have to pay anything.
To list your ebook on Amazon, you need to sign up for an account with Kindle Direct Publishing. If you already have an account with Amazon, you can use the same login information. Once your account has been approved and you provide all the necessary information, including a tax ID number, you can upload your book and cover. It generally takes about two days for the book to be approved, then it will be listed on the site and ready to sell. After that, you can check in for daily sales reports and view your accumulated royalties. As of this writing, Amazon pays 35% commission for ebooks priced less than $2.99, and 70% for ebooks priced $2.99 or more.
Barnes & Noble has their own service called PubIt! and it's for creating ebooks to be read on their Nook devices. The process is basically the same as the Kindle one in that you create an account or use your existing BN.com account, then upload your book and cover. They also approve the content and it only takes a couple of days. As of this writing, Barnes & Noble pays 40% commission for ebooks priced less than $2.99, and 65% for ebooks priced $2.99 or more.
Unless you are a Mac owner, the easiest way to get your ebook listed in iTunes for the Apple iBookstore is to go through Smashwords.com. It is an ebook publishing site that is affiliated with many different online publishers, including Apple. You will have to upload your book and cover then wait for it to be approved for the main site. If you wish to get what's called "premium publication" then there is also an approval waiting period. It took about a week for my book to show up in iTunes. Apple pays a 60% commission on sales.
If you use Smashwords, your ebook can also be approved for sale on sites like Sony, Diesel and Kobo. They also support Amazon and Barnes & Noble, but I prefer to manage them individually since the sales figures are updated more often.