GNOME Shell

GNOME Shell is intended to be a key part of the new user experience for GNOME 3. It provides many features including the following:
 * Launching applications
 * Opening files
 * Switching between open windows
 * Adding and deleting workspaces
 * Moving windows between workspaces
 * Dynamic system-related information display (including transient notifications)
 * Providing a flat list of user-account related actions
 * Logging out or switching the session, and stopping or restarting the machine

How to use it

 * 1) yum install gnome-shell

For Fedora 12, in GNOME, go to System → Preferences → Desktop Effects to enable it

Once GNOME Shell is activated, in the side bar, use the menu to disable it

Individual Components
Clutter - A high level openGL based graphics library and toolkit that is used in a number of places to provide smooth and flicker free animations and transition effects including Moblin, Media Center applications and in GNOME shell as well.

Mutter - A fork of Metacity (GNOME 2 Window Manager) with support for Clutter

Gjs - GNOME Javascript bindings relying on the engine from Mozilla. A number of GNOME Shell extensions are written in JavaScript using Gjs.

It seems to be missing a few features?
Yes. GNOME Shell included in Fedora 12 is a very early preview release. The first release of GNOME Shell intended for mass consumption will only be available in the second half of 2010 as part of GNOME 3.0. You can still provide any specific feedback by filing bug reports or requests for enhancement in http://bugzilla.gnome.org. If there any packaging specific issues, file them at http://bugzilla.redhat.com

What will the final design look like?
Some things are not decided yet but the general design is explained at http://www.gnome.org/~mccann/shell/design/GNOME_Shell-20090705.pdf