I have previously provided an in-depth explanation about NextCloud with Collabora Office Online and how we've installed it on Ubuntu 16.04. This is an update both of the process, and of the technology.
Dropbox is the best known of the end-user "cloud storage" services for documents, backups, and synchronising data among multiple devices, although now Google's Drive and Microsoft's OneDrive are functionally similar and are being heavily promoted and tied into all sorts of services.
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).