irst off, most Linux window managers are highly configurable. This applies more
to KDE than Gnome. In KDE, you can put the task bar on top or bottom. You can
add bars to any side. You can add or delete applets as you wish. You can change
the look of the bar, icons, cursors, fonts, window frames, and any of the
components of the window manager. You can use Gnome GTK themes in KDE. You can
add additional themes to KDE from: http://www.kde-look.org/
or for Gnome from: http://art.gnome.org/

If this isn't enough you can use additional programs such as Compiz-Fusion,
Avant Window Navigator, Emerald, Screenlets, Superkaramba, Gdesklets, adesklets,
gkrellm, kommando, and a host of other tools that add features or allow you to
dress it up. All of these will consume resources, but the sky is the limit.

If you want to go in the other direction you can start with a minimalist manager
and build it to suit your own tastes. Good choices for this would be Window
Maker, aewm, fvwm, icewm, openbox or Afterstep (which is like Litestep in that
they are both based on NextStep).

In Linux you have lots of choice. Windows comes with one window manager and few
people change it. Most alternative Windows window managers cost you money. In
Linux, they are all free, so you can download and customize to your heart's
content.

The ultimate in customization would be to build your own distro. Using a tool
like rPath you can even do this quite easily.