I recently encountered “Bablestone”, a blog with some carefully researched articles about typographic history. Rules for the long s (the ſ symbol, if you have it in a font) was the first one i read, but the site is worth exploring. Probably it would have been better to have talked about Conventions rather than Rules.
mentalfloss has a less scholarly and rather more popularist article that introduces the long s and several old letters Latin scribal abbreviations, although it’s probably worth reminding readers that æ and œ at least are still in use in British English, although less widely than thirty years ago.
Update: the Babelstone blog went away so i now link to archive.org for this page.