F4: Selects the Go To A Different Folder box and moves down the entries in the box (if the toolbar is active in Windows Explorer)
F5: Refreshes the current window.
F6: Moves among panes in Windows Explorer
CTRL+G: Opens the Go To Folder tool (in Windows 95 Windows Explorer only) Hopefully no one is using this :)
CTRL+Z: Undo the last command
CTRL+A: Select all the items in the current window
BACKSPACE: Switch to the parent folder
SHIFT+click+Close button: For folders, close the current folder plus all parent folders