xbanish (banish the mouse cursor when typing)

xbanish hides the mouse cursor when you start typing, and shows it
again when the mouse cursor moves or a mouse button is pressed. This is
similar to xterm's pointerMode setting, but xbanish works globally in
the X11 session.

One can easily start this automatically by putting "/usr/bin/xbanish &"
in ~/.xinitrc or some other WM/DE-specific startup file.