At first sight, the stuff at flossmanuals is basic - very, very basic.
Look at the openoffice.org "documentation" on flossmanuals. It explains what word processing and spreadsheets are. How many people out there need to be taught that? There probably are some, but how high are the odds that they know about the flossmanuals web site and how to read it?
There is plenty of basic documentation (GNOME and KDE), and there is plenty of high-level docs (man pages) for most packages. What's missing is the mid level, stuff that helps people between the "absolute newbie" and "guru" levels. And speaking about tldp, there are too many outdated manuals and HOWTOs around. The worst problem nowadays is that if you search the web for a problem, you are likely to find hundreds of links to outdated, often even misleading or wrong information.
What's the point in creating a new portal? Why not just improve the existing portals by adding and updating information?