A while ago I asked Are there any SciFi/Fantasy novels with a Whale Civilization at the core? The question was closed on account of it being "not for this site as it is a list question." I keep coming up with questions of a similar sort, e.g. "Is there a comprehensive list of science fiction containing some kind of star gate?", or "Books/stories featuring a gray goo apocalypse?" - things like that.
Other than obsessive Googling, is there any kind of cross genre resource that can be used for this kind of research/inquiry?
I realize this is also a list question -- but I am hoping it is a list question to end all list questions, so hopefully it will be allowed to live.