Poll with comments: skill tree.

Absolutely.
Also, it seems you can use a program that completely displays the map in a separate window.

Perhaps my opinion isn't very important here because I don't play online, but I'll still say something... The example is completely irrelevant. The program described in the topic performs an action that is already available to the player through legitimate means (writing down the locations of trees on paper or in a separate file and referring to it, or even memorizing them). But displaying the map is not possible. You can't write down the map for a random game on a piece of paper or memorize it, to put it bluntly.