What is the status of CiviCRM working with Drupal 8? And how can I help in terms of testing or funding this development?
There's now a beta version of a mostly automated installer at https://gitlab.com/roundearth/drupal-civicrm-project. You can also use it to add civi to an existing drupal 8 site as long as you installed drupal 8 using composer originally. See https://www.mydropwizard.com/blog/better-way-install-civicrm-drupal-8. (update Feb 2019)
You can find the code in its current state at https://github.com/civicrm/civicrm-drupal-8 (link updated Dec 2018)
There are bunch of issues on JIRA
There is a channel on Chat here
Active Development has restarted on the Drupal 8 version. It is possible to get it installed now, although it takes a slight different process than with Drupal 7.
Assuming you have Drupal 8.2.5 installed.
Download and install the 8.x-3.x-dev version of the Libraries module: https://www.drupal.org/project/libraries
Download the most recent version of CiviCRM 4.7 from CiviCRM.org , or if your a little more adventurous, the master branch from github.
Put CiviCRM core in /libraries folder of your Drupal 8 installation.
Delete the Drupal 7 modules from this download which would now be in /libraries/civicrm/drupal . You can delete the whole drupal folder.
Next get the 8.x-master branch of the CiviCRM Core drupal module
Put this in your standard Drupal 8 modules directory, /modules/civicrm
Now log in to your Drupal 8 site and goto /admin/modules
Enable CiviCRM, but do it by itself, do not enable any other modules at the same time.
This will attempt to install CiviCRM in the same database as your Drupal installation.
You will get some feedback if it has issues connecting to the database. If you get a "cannot connect to database" message, try the one line temporary fix documented in this issue: https://issues.civicrm.org/jira/browse/CRM-19835 There will be a fix soon for this issue
Now you will have CiviCRM installed. In my experience, there was an error at the root civicrm page at path /civicrm , due to something with the Dashboard. To fix this you must simply set the default organization and email address and From Name here: civicrm/admin/domain?action=update&reset=1
After that, all the CiviCRM pages will load, you will see the CiviCRM menu.
There are some issues that are being worked out, but at this point CiviCRM is usable. We need people testing this and documenting issues so that they can be resolved.
See answer from @jackrabbithanna for current status.
tl;dr : It's not yet production ready, and the list of things you can help on is in JIRA at https://issues.civicrm.org/jira/browse/CRM-17652?filter=23012 . Additionally, please create additional issues and mark Label them drupal-8.
Building on the previous work, Allen Shaw made some progress recently with assistance from Tim, Coleman and Nicolas at the Vail Colorado sprint hosted by Nicolas Ganivet.
The navigation menu and dashboard are now working.
For convenient assistance with developing, it is now possible to install D8 with CiviCRM using
civibuild create d8-master
Also, the new cividev environment builder ( https://github.com/civicrm/civicrm-buildkit-vagrant/blob/master/README.md) can configure a VirtualBox using Vagrant on your local machine with this or other builds supported by buildkit.
However, various issues need to be resolved before CiviCRM can be run in production with D8 as of mid-February 2016.
You could also try the RoundEarth distribution: https://gitlab.com/mydropwizard/roundearth-drops-8
"RoundEarth is a template for building a website for a nonprofit organization, based on Drupal 8 and CiviCRM."