In case anyone is interested in getting beryl / compiz going on CentOS-5 with an nVidia graphics card - here is the xorg.conf that I am using. The beryl packages are from centos.karan.org CentOS-5-Testing repo.

Section "ServerLayout"
	Identifier     "Default Layout"
	Screen      0  "Screen0" 0 0
	InputDevice    "Keyboard0" "CoreKeyboard"
EndSection

Section "ServerFlags"
	Option	    "AIGLX" "on"
EndSection

Section "InputDevice"
	Identifier  "Keyboard0"
	Driver      "kbd"
	Option	    "XkbModel" "pc105"
	Option	    "XkbLayout" "gb"
EndSection

Section "Device"
	Identifier  "Videocard0"
	Driver      "nvidia"
	Option	    "AddARGBGLXVisuals" "True"
EndSection

Section "Screen"
	Identifier "Screen0"
	Device     "Videocard0"
	DefaultDepth     24
	SubSection "Display"
		Viewport   0 0
		Depth     24
	EndSubSection
EndSection

Section "Extensions"
	Option	    "Composite" "Enable"
EndSection

--
Karanbir Singh { http://www.karan.org/ }