Make everyone site pages embeddable in forum posts
This could be cool. Then each "project" could have its own thread where people can communicate about updates.
Some sort of recently updated everyone page RSS feed
Maybe add a list that shows every everyone page?
Part of me likes the idea that there are hidden networks of pages that people have made that suddenly get linked to and everyone becomes aware of. But... this might be an idea that's better in the mind than in reality. Because if people don't know what pages have been updated then they won't see them and there won't be any collaboration which is the whole point.
To that end, it would be nice if you could see a listing of users and what pages they are editing. This could be cool but maybe a consequence of this would be that some people would feel followed and interrupted by other users. Generally it takes time to get your edit in a place where you're ready to hand it off to someone else, so maybe that idea isn't great.
But definitely something that says, "Here are the pages which have been significantly changed in the last x time."
Or "Here are the pages updated by x user since y time".
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Other than that, I think anything that incentivizes people to come up with a page idea and then actively try to get as many others to contribute to it as possible would be good. Also, anything that incentivizes people to find random pages in the site and give them more connections on other everyone pages.
I don't know how you feel about gamifying that kind of thing, points, etc. That maybe isn't the right way for this place but if it got people using the everyone site I think it's a good idea.