Timerover51
SOC-14 5K
If you go to the Project Gutenberg website, and type in science fiction as a search term, you get about a 1,000 possible downloads from a wide range of authors, and some complete early Astounding magazines. I am not sure if some of the stuff is really copyright-free, particularly the Harry Harrison, Andre Norton, and Alan Nourse stuff, but it is there if you want to look at if for inspiration or ideas.