Compiz Fusion is cool but not all PCs can run it well, on counterpart Metacity WM still doesn't implement any effect (horrible minimize effect apart).
So what to do for a transparent, drop shadows enabled, usable Desktop?

Xfwm4 is the answer, it integrates itself well in GNOME and it offers a nice gui to configure the effects. Cairo-clock and awn dock run with transparencies because this window manager has the composite already built-in.

(Drop shadows + transparencies + awn on a S3virge!! )

Installation

Just 2 dependencies.

sudo apt-get install xfwm4 xfce4-mcs-manager

Try Xfwm4

killall metacity && xfwm4

To enable effects run xfce-setting-show and go in the Compositor tab
If it satisfy you, is possible to make it default

Replace Metacity

gconftool --set --type string /desktop/gnome/applications/window_manager/current  "/usr/bin/xfwm4"
gconftool --set --type string /desktop/gnome/applications/window_manager/default  "/usr/bin/xfwm4"

You can also set the wm path with gconf-editor

Notes

Xfwm4 doesn't use Gnome global shortcuts, You need to redefine them.
If Metacity still remains the WM, you need to delete it from the session.