In terms of adventurers, I'd love to see some thing along the lines of Dark Space by Monte Cook for the old Rolemaster system. It had dark eldrich creatures, space, science fiction, fantasy, undead, and all sorts of other goodies that just scream create campaign based on this! Otherwise, something like Babylon 5 where an ancient darkness is rising. Of course, now that CoC has d20 stats to it...
A book of vignittes might be interesting too. SOmething that pits the players are pirateers with the characters hunting down progressively tougher foes until they fight the master mind.