Read the Docs supports a number of custom domains for your convinence. Shorter urls make everyone happy, and we like making people happy!
Every project has a subdomain that is available to serve it’s documentation. If you go to <slug>.readthedocs.org, it should show you the latest version of documentation. A good example is http://pip.readthedocs.org
If you have your own domain, you can still host with us. If you point a CNAME record in your database to the subdomain for your project, it should magically serve your latest documentation on the custom domain. Using pip as another example, http://www.pip-installer.org resolves, but is hosted on our infrastructure.
You can also use <slug>.rtfd.org as a short URL for the front page of your subdomain’d site. For example, http://pip.rtfd.org redirects to it’s documentation page. We’re looking for more fun ways to use this domain, so feel free to suggestion an idea.