The names in the haskell.org domain point to a set of machines. The bulk of those machines are now cataloged on the Haskell Phabricator Wiki
Certain machines had been made available for community hosting in the past, and many still exist on community.haskell.org. However, given the rise of new options for hosting, we are discouraging the use of these servers, and would like to help those now currently using them to find a way to host their content elsewhere. See the February 2015 blog post The Future of Community.Haskell.Org for more.
2 Policy on adding new subdomains
We limit the addition of new subdomains to haskell.org to minimise unnecessary proliferation of subdomains and to try to keep the haskell.org domain reasonably well organised, while still helping people do useful things with it.
The policy has been that new subdomains are to be used for services rather than content.
So for example a Haskell graphics related website would normally go at http://www.haskell.org/graphics, rather than http://graphics.haskell.org.
In contrast a service like hackage does merit its own subdomain.
In either case, adding either new services or subsites is fairly rare and such requests will be considered on their own merits, on a case-by-case basis.