My fifteenth book will be available on Amazon and Barnes and Nobel within a week or two. All but one of those fifteen have been published using Amazon's CreateSpace. In fact, I have written a guide to using CreateSpace titled Self-Publishing with Amazon's CreateSpace: A Resource Guide for the Author Considering Self-Publishing.
CreateSpace has a lot of features available to authors who want to use CS to self-publish. Depending on what you want, CreateSpace will provide you an ISBN and will be the publisher of record or you can provide your own ISBN and CreateSpace will simply act as your POD printer and distributor of your book. CreateSpace recently added author services as part of the offerings and services for authors provided by the company.
The entire process starts with creating an account and then working through the steps required to create the publishing records and upload the files to publish your book. For an additional $39 fee the author can purchase the Pro Plan and I strongly urge you to do so. The purchase of this plan will dramatically lower the cost per copy and increase the percentage of the sale of the book Amazon for the author. In other words, you will make a lot more money in the long run by spending $39 up front.
The details of the step-by-step process are explained in my book which also contains considerable reference material designed to shorten the learning curve for an author exploring self-publishing and desiring to learn as much as possible. There is a lot to learn if you plan to become a true self-publisher with an eye to actually making some kind of a profit and not venture into an expensive hobby.