I think other people should know the sorts of skills they'd want to have to get around in unfamiliar situations--a lot of which is meta-information. I think having lots of specific knowledge is not nearly as important as knowing how to remedy the gaps when you find them, or at least being able to find workarounds. So things I think everybody should know: how to usefully use a search engine, identifying which resources are most likely to help you solve your problems, how to ask questions of people so they will give you good answers, summarizing and extracting main ideas from information sources. (There are lots of basics I think fall one level below that: doing practical math, using maps, essential self-care and first aid, etc.)
I've taught someone the basics of algebra (something else I think everyone ought to know) via IRC; he was a programmer but had a spotty educational background and never really understood the math. (How can you be a programmer without understanding algebra? I don't know; that's what those of us in the channel at the time asked him...) It took some group effort to convince him that he was not going to be hopeless and that math did not have to be painful, and after that it was fairly easy going.
Related: I'm often shocked that people don't use common sense to handle situations where they don't have complete and explicit knowledge. It seems that some folks don't have the confidence to try muddling through in unfamiliar situations.
Languages are a good example.
The only foreign language I've actually studied systematically in school is French. And yet: I can understand a newspaper article in Spanish, get a printer that's stuck in Dutch language mode back to English, use an Italian book as a reference for an art history paper, understand the lyrics...
There's been a recent heavily upvoted and profusely commented post about things people want to learn. It's close to having so many comments in a single day that it should probably have a part 2.
However, the subject seems to inspire thoughts about what *other* people ought to know, and while that's got a good bit of overlap, it's emotionally rather different.
So, what do you think other people ought to know? Any theories about why they haven't learned it already? Any experience with getting someone else to learn something when it started out as your project rather than theirs, especially if the other person was an adult?