Blog of Holding, home of the excellent D&D with Michael Mornard posts, just released a mashup of the OD&D setting I detailed in this blog with an idea from Jeff Grubb about a world overrun with evil where most humans have taken to flying ships. This has shades of Burroughs to it, so I most heartily approve. Check it out.
One setting I've been thinking a bit about is Dune. There's a documentary coming out this year about the attempt by surrealist cult director Alejandro Jodorowsky to make a Dune movie basically as a sci-fi acid trip with lots of symbolism, but he assembled massive amounts of talent to get it made. Of course that blew the entire budget and some of the people he'd brought together went on to make Alien, while David Lynch more or less failed at making a Dune movie. The world and its aesthetic always appealed to me, though only really Dark Sun among D&D settings ever scratched a vaguely similar itch. It would be an interesting exercise to stat out melange (the Spice), sandworms, and Fremen for D&D; from later volumes, no-rooms would be tremendously valuable, as would people immune to prescience.Not too hard if we assume a bigger desert in a D&D planet.
Science fantasy seems to be a natural fit for old school Dungeons & Dragons. We've had touches of it for a long time: Barsoom in OD&D, Temple of the Frog in Blackmoor, Tékumel, Jim Ward's Metamorphosis Alpha and Gamma World, Wilderlands of High Fantasy, Arduin, S3 The Expedition to Barrier Peaks - the list is not short. Holmes mentioned his Dreenoi PC and this is just a taste of the possibilities. I think that this was a phase as much in fantasy as anything else; as worldbuilding rather than imagination became the word of the day, flagrant discontinuities such as lasers or force shields in a fantasy game had to go away. (Though there's magic in some popular sci-fi, Star Wars being fantasy in most regards.)
This is something I've touched on before and will again. But really check out the mashup idea from Blog of Holding, I think it's onto something there.