About a year ago I saw that a big wall-size roll-up calendar was being thrown away at work. At first I was only interested in the large mailing tube but I looked at the calendar and saw it was the dry erase type. The important feature was that the back was a plain white surface. I thought that I could mount it on a piece of plywood and have a rather large white board for the darkroom. At first I hung it picture style and wrote solution mixing dates and proportions for various developers to get the desired final volume. This was OK but it wasn’t really used to it’s full potential. Later I wanted the wall space for some shallow shelves and had to move it. By this time the only unused surface was the back of the door next to the enlarger table. So I mounted firmly against the door (on the darkroom side, of course). I would place reminders there and stuff like that, useful but no big assistance. While enlarging last month, I was printing a particularly complex photo and kept having to change the printing notes in my ring binder darkroom book. I looked over at the board and transferred the information there. It was a great move.
Now I can have a large sketch of the print and can quickly add, subtract or change any instructions. It is easily visible from where I stand while at the enlarger and, most important, it is quite legible under the safelight conditions unlike the pencil marks on the pages of a small binder.
This may not seem like much, but this was one of the best improvements I ever made to the darkroom. If you have the space, I really encourage you to install one.