As everyone else has said, you can host multiple primary domains on the same account without any additional hosting fees. Again as others have said, if you want additional primary domains, you will have to pay the annual $9.95 domain registration fee for these domains. An example of this is that you've registered sleeptodream.org as the one domain registration that comes with your hosting package. If you also want the domain sleeptodream.com, you will have to pay $9.95 a year to register that domain name. You will be able to host both domains under your one hosting account at DreamHost.
On the other hand, if all you want to do is have www.sleeptodream.com, forums.sleeptodream.com, blog.sleeptodream.com, gallery.sleeptodream.com, etc., then you can do all that without any additional fees. You just need to create hosted subdomains in the DreamHost control panel and you're good to go.
Free unique IP and $67 off with promo code [color=#CC0000]FLENSFREEIP67[/color] or use [color=#CC0000]FLENS97[/color] for $97 off. Click here for more options