I've been looking for the infamous Kourovka notebook, but there are apparently others.
Recall the Kourovka notebook is a collection of open problems in group theory. There are other notebooks with open problems in other fields.
For example, the Dniester Notebook [usask.ca] (pdf, 56 pages) has problems in ring theory.
The notebook stopped being published years ago. Now it's been open sourced.
The Sverdlovsk notebook stopped publishing back in 1989; it was a collection of open problems for semigroups, but it cannot be found.
Other problem notebooks might exist too, but I am unaware of them...