Google Docs are great for allowing people to collaboratively build a document, with the ability for people to suggest (and discuss) changes and view revisions and a variety of other useful behaviours. At present, I'm sad to admit, CollaboraOffice isn't quite in the same level (although it's catching up quickly!).
A few weeks ago, I got an unexpected (but very flattering!) request from a friend and colleague's son, Felix. He wanted to interview me about my work (at 11, he thinks he might want to become a software developer, too, when he's older) as material he could present at an up-coming PechaKucha session at his school... Wow, we didn't do PechaKucha when I was a kid :)
Update 2021-11-08: this post is now getting a bit long-in-the-tooth, and I need to update it to use up-to-date components. It might still be useful to folks, but use it with caution. Also, please note, we're using NextCloud with OnlyOffice (the open source community edition) these days. Update 2023-06-14: Here's a new tutorial for Ubuntu 22.04!
LimeSurvey is an open source survery tool, functionally similar to far more heavily marketed proprietary tools like SurveyMonkey and Google Forms. It's a very mature, fully-featured system. You can either use the reasonably priced hosted service available on the LimeSurvey site, or you can host your own, holding your own data and collecting your own analytics if you prefer. The only cost of hosting your own is your time to set it up and any costs associated with your hosting environment (which, today, can be negligible).
Here at the OERu, we provide a service, attached to all of our online courses (and available to all of our partners - or anyone else for that matter) which allows anyone involved in those courses to communicate with their peers from any one of a dazzling array of online "places" with WikiEducator Notes (aka WEnotes). The entire system is free and open source software (FOSS).
One of the OERu's most compelling technological capabilities is the set of internally developed open source tools that allow us to automatically transform and inject a collection of MediaWiki content on WikiEducator (usually in form of micro-courses) making up a course into a mobile-friendly, easy-to-navigate WordPress site, usually situated on OERu's Course WordPress Multisite implementation.
A few months back, I posted instructions on deploying Rocket.Chat and Wekan instances (and their mutual dependency, MongoDB) individually. Since then, I've spent some time with Docker Compose, a set of scripts which help you to define, build, and manage a set of Docker containers. Docker Compose is a thing of beauty. This is the way I now deploy Rocket.Chat, Wekan, and MongoDB together.
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).