Several common used virtual effects to prettify your Ubuntu

First you need to install compiz.
Then open CompizConfig Settings Manager to enjoy your works.

1.Windows Shadow

2.Top Panel Transparency&Launcher Panel Transparency

'Experimental' Tab --> 'Panel Opacity' item. The value is from 0 to 1.
'Experimental' Tab --> 'Launcher Opacity' item. The value is from 0 to 1.

You can get effects:

3.Menu Transparency&Windows Transparency

On 'Opacity Tab' --> Click 'New' button and add "DropDownMenu", "PopupMenu" and "ToolTip" and adjust corresponding value to an integer below 100,  its range from 0 to 100.

This function is very powerful. You can try clicking plus sign button, add more things for it and explore.
Commons windows transparency are also configured here. It provides several ways to specify which windows are transparent. I used to set windows transparency, but later I removed it. I found that was simply test my eyesight.

4.Title Bar Transparency

Open 'Configuration Editor', find directory '/apps/gwd', edit two keys 'metacity_theme_active_opacity' and 'metacity_theme_shade_opacity'.

 See the title of terminal window