In GNOME 2.22, included in Ubuntu 8.04, the default Metacity window manager has compositing built in. This means that you can get your eye candy effects without switching window managers!
Metacity won’t give 3D effects on the same level as Compiz, but it’s much faster and less resource-intensive. The main advantage of using Metacity’s compositing is that you can run applications such as Screenlets, Awn, and GNOME Do that would otherwise need Compiz for their eye-candy. In addition, you get shadows, max/minimize animations, and shaded Alt-Tab effects.