UPDATED: This’s only working for the apps that are downloaded from AppStore. If you want to remove any icon, please use this little & free tool: LaunchPadCleaner!
LaunchPad is new in Lion, and it’s a simple way for you to navigate and open your applications, like you do it in iPhone or iPad.
Whenever you install a new application, there will be an icon in the LaunchPad. This is the trouble if you have too many application installed, but only want to keep some of them in LaunchPad.
Fortunately, there’s an easy way to remove the icon from LaunchPad: Press the combination Ctrl + Option + Command and while keeping them pressed, click on the icon. That shortcut will be removed from LaunchPad but still be kept in Applications.