At the OERu we have two separate instances of market category leading Discourse Forum: one for OER partner and contributor collaborators and the other for learners. These days, online forums are seen as a bit old-school: fuddy-duddy. From my point of view, however, Discourse is "Forum-NG" (a Next Generation forum).
(Update 2017-05-24: see an easier way to run Wekan, Rocketchat, and MongoDB) You may not have all of these installed, but if you're running Wekan or Rocket.Chat based on our instructions, you'll also have MongoDB, and the need to keep them all up-to-date to benefit from their rapid development processes (quick bug fixes and new and improved features every few days!).
Wekan is an excellent, easy-to-use "kanban board" project management support tool, suitable for all manner of projects. For those who have used the highly marketed Trello kanban service, Wekan is functionally similar open source alternative that organisations can host and control for themselves. They can also enhance it in whatever ways they are moved to do so. We encourage our partner institutions to consider this path as a way of reducing costs as well as increasing freedom and privacy.
The OERu is committed to using free and open source software (FOSS) for all our technical infrastructure to the extent possible. We're doing pretty well in living up to that principle, but there are a few crucial technology areas where we have not yet found a sufficiently usable or mature FOSS option. This post identifies those exceptions, as they stand in September 2016. Despite being grateful to have these proprietary applications available to us, we will replace them with FOSS in each case as soon as a viable option is available!