The new domain thedebianuser.org is still in its infancy, but at least its focus is pretty clear: it targets Debian users, which includes pretty much everyone from new converts to Ubuntu users to Debian Developers
Read about it at LX'er
Until now, I just set up a blog, and I welcome everyone who has something Debian- or FOSS-specific enough to post it there. For the more short-lived things, we could add a planet and so aggregate whatever people are writing on their own pages. A Wiki? No – that exists on the debian.org domain already.