There is Gnome, there is KDE (more configurable), and there is Xfce (lighter). And there is my custom desktop environment based on Fluxbox window manager :-p.
Window manager : Fluxbox
Taskbar, Traybar : Built in Fluxbox
Keyshortcuts management : Built in Fluxbox, + lineak for multimedia keys
Pager : fbpager
System monitor : Conky
Network manager : gnome-network-manager
Power manager : gnome-power-manager
Clock : stickytime
Screensaver/Lock : gnome-screensaver (with its wonderful “leave a message” feature!)
Graphical sudo : gksu