Openbox is lightweight window manager. I installed it on my gentoo, i really liked it. Openbox starts in blink of an eye my gentoo.Openbox just takes seconds to install in any distro. It comes around 500 Kb download size. I have been using GNOME environment in Ubuntu. I feel like GNOME is too slow in my system. I installed openbox and used with gnome session. It is really faster than complete GNOME session. You can change the session from the GDM option menu. Select, Openbox with GNOME session. You’ll get gnome panel, nautilus and other gnome apps with faster openbox window manager without losing the most of the gnome look & features. Openbox rocks !!!
sudo aptitude install openbox
and here is the screenshot for you ;)