Since I'm pretty sure the Dune d20 idea is long dead, I second the motion for things like
-- deck plans for various ships
-- starship combat rules
-- a series of random charts for generating planets on the fly
-- rules for moving and combat in alien environments
-- high-tech but still believable technology (i.e. no transporters or time travel); basically take the new Battlestar Galactica as an example ... except for the FTL drives on the ships, the technology is advanced but still realistic.