Assigning shorcuts/functions to keys

Gnome Desktop Environment maps all multimedia keys by default and you can re-assign those with gconf-editor and Keyboard Shortcuts.

In KDE, you have to do it yourself.
Execute xev command and note down keycode of key. Execute xmodmap command to assign whatever application/function you want to invoke.
Code:

xmodmap -e 'keycode 115=Menu'
xmodmap -e 'keycode 174=XF86AudioLowerVolume'
xmodmap -e 'keycode 176=XF86AudioRaiseVolume'
xmodmap -e 'keycode 160=XF86AudioMute'
xmodmap -e 'keycode 162=XF86AudioPlay'
xmodmap -e 'keycode 162=XF86AudioPause'
xmodmap -e 'keycode 161=XF86Calculator'
xmodmap -e 'keycode 178=XF86WWW'
xmodmap -e 'keycode 237=XF86AudioMedia'
xmodmap -e 'keycode 236=XF86Mail'
xmodmap -e 'keycode 235=XF86MyComputer'
xmodmap -e 'keycode 230=XF86Terminal'

Save above code in file, let say, key_map.sh and move it to ~/.kde/env folder. It will be autoexecuted on every login.
Edit any/all shorcuts according to your needs.