At least five years ago, I had an idea for a website that was a database of plot elements used in science fiction books and movies, creating lists of the works that use each element. So one entry might be "sentient space ships", and there would be a list of books that feature them.
This was meant to be a definitive archive... I distinctly remember this because shortly thereafter I found a site that was already doing it! I believe I emailed the site's author about collaboration and never heard back. (It was before the days of crowdsourcing, or anyway, I don't think it had user-generated content.)
The point is that now I can't find this site. Does anyone know where I can find it, or have any suggestions about what I might be remembering?