BBcode (a sort of HTML-like mark-up, that you are free to use in message posts) also you to make stuff
*REALLY BIG*
or even
...although that (advanced inline graphics) is probably a discussion for another day. But hyperlinks are supported, you may attach proposed agendas and reference documents, images and/or video, and people may themselves upload and download stuff.
And it can all be "Admittance Restricted" if that is your desire... ergo postings may be visible only to users who are vetted, bona-fide participants in your group or tenant association.
...