Can I repost something interesting I saw elsewhere?

Maybe, sort of, but probably not. Post about it, sure. Cool stuff already posted elsewhere can be quoted  (enough to provide some context to get a sense of it) and then linked to the source. Add some original content or perspective of your own. Something more substantive than, “Cool … read this.” For example, if you want to know what other people think of it, tell us first what you thought of it.