My personal experience in online collaboration extends to using learning management systems, chat platforms and document sharing platforms (and email). These experiences have always been complemented by having face-to-face meetings from time to time.

I used two major platforms to communicate for collaboration with my teaching assistants: WhatsApp and Slack. I find each of them had some advantages, namely WhatsApp seems to be popular with more people and they check the messages more often. However, it does not give you any easy way of tracing different discussion threads that take place simultaneously. Slack is meant as a platform for communication in software development groups, and different integrations with popular tools (GitHub, Google drive) that help with collaboration. Under the same organization, you can host discussions for multiple groups (with different members), one-to-one discussions, and different channels (that might correspond to different topics). Slack makes keeping track of the discussions much more easy.

We commonly use file sharing platforms, and we collaboratively edit documents. We have a review process that helps with identifier problems very early. Basically each document is prepared by a person (in-charge), and it is reviewed by two other people at least, sometimes more. In addition to content/material preparation, we use our communication (chat) group to share interesting reads on topics related to the topics that we teach. These materials end up generating lots of discussions, and we get to learn a lot from them. 

Another type of collaboration I sometimes use is, in class, I use class interaction tools to ask students questions, and we can see real time their input. This helps a lot because it gives me the opportunity to explain additional content that I would not have mentioned otherwise. 

With an increasing number of online and free-to-use tools for collaboration and cooperation, learning in communities became an easy task. However, we need to exercise care in the way we choose and use these tools.