I just found out from the blog of mathematician Terence Tao about Scholarpedia, which is apparently trying to fill in the space between Wikipedia and academic encyclopedias. The goal is to be more authoritative than Wikipedia, and more responsive and current than other academic encyclopedias. Right now, this space is filled quite well in philosophy by the Stanford Encyclopedia of Philosophy, though I can also imagine a use for something in which multiple people can update and edit articles. But right now, Wikipedia seems quite spotty on philosophy (it seems quite good on math and physics, though perhaps not so much so for people who aren’t already well-educated on the relevant topics).
Since it’s quite new, there’s a lot that’s still under development, and there are especially few articles on philosophy so far. But if philosophers get involved in this early enough, it could become quite useful. It looks like they’re commissioning an article on philosophy of mind from Jerry Fodor. The article on the mind-body problem looks like it needs some revision at the moment. And the article on intentionality looks like it could use some philosophical additions – right now it seems to define intentionality as a property only of brains. (Even if this is a technical use of the word, it seems relevant to mention the different but related technical use by philosophers.)
Also, it looks like the way policy is determined depends on who has made edits that previous moderators found useful, so making some good edits now could make sure that some philosophers have a say in how this develops.