The Open Source content management system PLONE runs the newly released NASA Science web site.
The site has something for everyone (researchers, educators, kids, and “citizen scientists”). The Plone seems to be working quite nicely.
Some of it is still a little rough. The Space Calendar link seems to be broken, and the email to the “responsible government official” for the site (who, by the way, is Greg Williams) gets you an email to “email@example.com” …
There appears to be a number of distinctly different ways to navigate on this site, including a main in-your-face graphical orientation to four main topics (Earth, Heliophysics, Planets, Astrophysics) each of which leads to a page with a “Big Questions/FocusAreas/Missions” dynamic side bar menu. (These sub-sub topics, big questions, missions, etc., are re-grouped on thier own pages accessible from the top menue as well)
Many of the links seem to lead to fairly specific questions or NASA programs enveloping lists of missions that address those questions or are run by those programs, or to the missions themselves with a sidebar indicating what the “related big questions” are.
The site has actually done a pretty good job of assembling, correlating, and cross-indexing the myriad components of NASA.
So what about the NASA.gov site? This looks to me like an eventual replacement.