How to add menu items to the start menu of your Raspberry PI?

The menu files for the start menu are stored in the directory:
/usr/share/applications
(with the .desktop extension)

Let’s say you want to add Processing to the ‘Programming‘ section of the start menu:

• create a 32 x 32 pixels .png icon for the application and save it to
  /usr/share/pixmaps/
• create a new desktop file:
  sudo nano /usr/share/applications/Processing.desktop
• enter the following lines of text:
  [Desktop Entry]
  Type=Application
  Name=Processing
  Comment=Processing programming language
  Icon=/usr/share/pixmaps/processing.png
  Exec=/home/pi/processing-1.5.1/processing
  Terminal=false
  Categories=Development;
• restart the lxde environment by typing:
  lxpanelctl restart

Thanks to:
http://lkubaski.wordpress.com/2012/06/29/adding-lxde-start-menu-and-desktop-shortcuts/