Also, at least in explorer, in the tree view, pressing left repeatly closes the folder you're in (if it's expanded) or moves to the next parent (if it's closed).
Alt-Numblock-* will open the next level of all sub folders under the selected one.
Whooa, this one is nice! Appears to be standard treeview controls too, works in an app I work on as well, except it appears to do fully recursive expansion. Not recommended on unlimited dynamic nodes..
Left to close trees, right to open trees, up and down to move through the list (as it operates as one long list for up and down, not as a tree).
Regedit became so much nicer with this, especially after adding in the fact that you can start typing to jump to the next occurrence of whatever you type.