I have found it worthwhile to keep a bunch of org mode files about stuff I get interested in. They become progressively more useful as search engines get worse: if I find an interesting page and make a mental note of it, I probably won't be able to relocate it by remembering a few keywords as was formerly possible. So now I make a point of saving the link and ideally a quick summary in an org file. It's fairly practical to find stuff that way using emacs search commands (I could imagine improvements). But the individual files aren't particularly organized, they are just chronological (append new stuff to the end), with occasional updates or cross-links in the middle. I don't need anything fancier. I sometimes post the notes online (Org html export) and other people find them useful despite their near-total lack of structure.
This is not too different than the old fashioned way of reading books for English class: keep a yellow pad alongside of the book as you read, and as you read each page, note down the main points made on that page, along with the page number. Then when you have to write your class paper, it's pretty easy to go back over your notes to find what to use from the book, and to find it again in the book and cite it with page numbers.