Since quite some time we as student council are running CodiMD as an internal service. You can create shared notes, presentations and many more things while collaborating in real time through an relatively easy to use UI.
We now opened an installation of the tool to the public: codimd.mathphys.stura.uni-heidelberg.de
If you have any questions regarding the tool feel free to write an email to root@mathphys.stura.uni-heidelberg.de.
Happy Hacking,
Your Student Council