I seem to remember that linked lists, recursion, pointers, and memory management are all good examples of stumbling blocks - places where the aspiring programmer typically ends up spending significant time trying to understand a concept before moving on and improving, and many end up giving up and not improving.

I'm looking for a complete/comprehensive list of these types of stumbling blocks, in rough estimated order of difficulty to learn, with the goal of making sure that an educational program for programmers is structured to properly guide students through them

Is this information available somewhere? Ideally, the difficulty to learn will be measured in some sort of objective manner (ie, % of students which consistently fail to learn the concept) What sources are most appropriate for obtaining this information?