These two commands set keybindings for horizonatally and vertically maximizing a window. Most of the time when you maximize, you only need one of the two dimentions to be bigger.
$ gconftool-2 --type string -s \ /apps/metacity/window_keybindings/maximize_vertically \ '<Ctrl><Alt>v' $ gconftool-2 --type string -s \ /apps/metacity/window_keybindings/maximize_horizontally \ '<Ctrl><Alt>h'