Something I have always found useful as a DM is a quick reference sheet containing all the vital statistics and abilities of the player characters. It's much faster to glance over my own cheat sheet than to ask a player for the information I'm seeking. It also helps prevent tipping off the players as to what might be coming up soon.
Although there are lots of DM playing aids out there, I couldn't really find anything that suited my needs for my current B/X D&D campaigns on Roll20. So, the only thing to do was to make my own!
In the hopes that it might be useful to other DMs, I am making available for download the B/X D&D Adventurers Log I am now using in my own campaigns. If you use this in your own game and subsequently come up with recommendations for improvements, I'd be glad to hear them!
B/X D&D Adventurers Log