Links

• Using xmodmap
• Natural scrolling in the synaptics driver
• List of Keysyms Recognised by Xmodmap
• How to retrieve scancodes
• Multimedia Keys article
• Mapping unsupported keys with xmodmap
• Ubuntu Lucid
  • Lucid supports input device hotplugging and uses xkb to configure keyboard options. Rather than using xmodmap, keyboard layout options should be modified in System -> Preferences -> Keyboard -> Layouts -> Options. These are per-user settings, unless you click "Apply System-Wide".
• Some hints about xmodmap(1) and the X11 keyboard model

Example

keysym space = space underscore