Saving Firefox plugin to disk

If you discovered an awesome Firefox plugin and you wish to share it with your friend, you can save it to your hard disk and install it in your friend's pc without to download it again.

The method is simple. Instead of left-clicking the "Add to Firefox" button,right click on it and select "Save Link As". To install it into another firefox just press CTRL + O and browse the plugin file(whatever.xpi).