A list of plugins is now available at https://docs.pytest.org/en/latest/reference/plugin_list.html in the official pytest documentation.
This website was an excellent learning tool and provided a nice list of all pytest plugins available. It implements a non-trivial workflow where we execute jobs on Travis that test each plugin for compatibility against some pytest and Python versions, along with their descriptions (more info).
Maintaining the website has a non-zero cost in time, and also things are not perfect, so I decided to just stop maintaining it, given that the new list of plugins in pytest documentation already gives a good overview of the plugin ecosystem (see #66 for more details).
The website will be shut down sometime in the future, but the github repository will remain there for reference.
The source code of the website, for those interested, is available at github.com/pytest-dev/plugincompat.