My DM board for Dungeons and Dragons sessions. There are some quick references, random magic items, and quick hints about the rules (some of them are homebrew). The most useful element for me is the random NPC picker, where I use Sketchgoblin pictures, because that's a nice variety of characters, each one with some unique, visible attribute. The rest is part of the improvisation.
https://www.sketchgoblin.co.nz/
I recommend it for Dungeon Masters, and each RPG system can use some elements of it, but it is optimized for Dungeons & Dragons sessions, where at least the DM has access to DnDBeyond. (That's actually a great tool to build your own encounters, I just prefer my notes to be organized in Miro.)
dndbeyond.com
