Being a N810 user, I was able to contribute some to the Maemo Basics page but I hope that somebody starts filling up the N900 section.

I would suggest that one major section of the N900 entry (or even a section on the front page) should be N900 software. This should be divided into three sections: what the N900 can do out of the box (ideally this will be a series of links to Nokia documentation pages); what additional software is available for the N900 in the app store (here the documentation starts to get a bit spotty); and what is not yet available but is being worked on. For people who have gotten past the first steps with the phone, I suspect those are the questions they are going to want answered.