xfonts-100dpi xfonts-75dpi
Unfortunately currently apt doesn't update the font path, so you need to do so manually:
xset +fp /usr/share/fonts/X11/75dpi:unscaled
xset +fp /usr/share/fonts/X11/100dpi:unscaled
xset fp+ /usr/share/fonts/X11/75dpi
xset fp+ /usr/share/fonts/X11/100dpi
xset fp rehash
Taken from the ubuntu forums here.