There are several print-on-demand companies that provide economical printing of your paper back books, should you choose to do so. Many people who publish ebooks never feel the need to have paper books, but others do. We won't go into great depth on this subject, but here are some links:
Added 5/15/12 - Matt Iden's Blogs on:
Printing Your Book with Createspace Part 1
Printing Your Book with Createspace Part 2
Printing Your Book with Createspace Part 3
This is who we use; we've found them to be very user-friendly. Formatting a paper book is more detailed, so many writers pay someone to do the formatting professionally. You can find links for paper book formatters on the Formatting page. If you are good at creating PDFs, you can likely do this yourself and save yourself the money.
Covers for paper books must be formatted specifically for Createspace printing as well since a paper book cover requires a spine and back cover - you will find detailed instructions on the website. Many authors pay a cover designer to do this extra work since it is detailed and book size-specific.