10 + GNOME Shell extensions that I found useful

According to GNOME site GNOME Shell extensions are small pieces of code written by third party developers that modify the way GNOME works. If you are familiar with Chrome Extensions or Firefox Addons,GNOME Shell extensions are similar to them.
 The below  GNOME Shell extensions are some of the must  haves on any GNOME 3.X desktop. If found that the below extensions are novel and at the same thime extremely useful . All the extensions mentioned are tested on GNOME 3.2.1 / openSUSE 12.1 / SeaMonkey .The extensions site has been a huge hit with the GNOME users.

Pre-Requisites

==>Ensure that Community repositories are installed and also the following packages are installed
        ==>gnome-shell-browser-plugin - The GNOME Shell Browser Plugin
                provides integration with gnome-shell and the corresponding
                extensions repository
        ==>gnome-shell-extensions - GNOME Shell Extensions is a collection
                 of extensions providing additional and optional functionality to
                GNOME Shell.
       ==>gnome-shell-extensions-common - This package provides files
               common to several GNOME Shell Extensions
       ==>gnome-tweak-tool - GNOME Tweak Tool is an application for
               changing the advanced settings of GNOME 3.

 ==>One needs a gecko compatible browser like (SeaMonkey or Firefox) to install the extensions from the GNOME Shell extensions.
Manage Extensions
When one installs the extensions from gnome site they get installed in "~.local/share/gnome-shell/extensions" directory path  by default.

  The source code installed here can be in fact customised  which is pretty awesome. I did try and customise one of the extensions,the process which I have described below.
You can manage(Delete / Turn On(Activate)/TurnOff (Deactivate)) the Shell extension using Installed Extensions page.

 Alternatively ,You can manage the installed extension using Advanced Settings tool (or) gnome-tweak-tool

10 + / Ten plus Extensions that rock

==>Alternative Status Menu
This cool extension brings the Power Off menu to the User Menu .This eliminates the nee to keep pressing Alt button to access the power off button when one wants to shutdown their machine.Before activation of this extension you cannot see shutdown or power off menu.

 After activation of the extension you can see the shutdown menu

==>Remove Accessibility
Helps to remove the generally unused accessibility menu from the top bar or panel in Shell desktop unless otherwise you need to access the onscreen keyboard regularly.Before installing this extension you can see the accessibility tool.

You don't see it after activation of this extension

==>Media Player Indicator
This extension allows one control ( playback ,volume ) the multimedia players like banshee.You can navigate your playlist without switching to the player

==>NetSpeed
Shows the speed at with internet is working when you are browsing the net.

==>Coverflow Alt Tab
Move over Alt Tab switcher Coverflow Alt Tab is here.Brings back memories of gnome 2 desktop effects.Move-over Alt Tab,Coverflow is here.Coverflow unlike Alt Tab based switcher shows multiple windows of same application without collapsing them.When using Alt Tab based switcher you nee to use Alt+` along with Alt+Tab to switch between two windows of the same application
Alt+Tab Switcher

Coverflow Switcher

==>ToDo List
You can maintain a simple to do list.You can jot down things you need to do without any hassle.

==>Shutdown Timer
This extension is an ideal tool if you want to schedule your Power Offs on you machine.If you have a download running and you want to lave your system unattended and you want the machine to shutdown after download then this is the ideal tool for you

==>Recent Items
This extension can display the latest accessed files on your desktop.You can clear the recent list of documents and files too.

==>NothingToDo
If you don't use the calendar tool on evolution to keep the appoints then the calendar in the top bar doesn't require such a large window to show all the appointments.This extension would help in making the calendar cuter.
Calendar Before installation

Calendar After installation

==>Search Firefox Bookmarks
This is an extension which helps one search for the bookmarks through the GNOME Shell Activities window.This extension was originally meant to e used for Firefox.But  don't use Firefox and hence wanted to tweak it to work with SeaMonkey.You can install SeaMonkey for openSUSE 12.1 using this link
I got the Firefox bookmark search extension to work with SeaMonkey by editing the "extension.js" file present inside folder path "~.local/share/gnome-shell/extensions/searchfirefoxbookmarks@ciancio.net/". I replaced all occurrences of the string firefox with SeaMonkey in that file using gedit an viola,it became SeaMonkey search extension.

==>Inhibit Applet
This can prevent you monitor from switching off / prevents monitor from going into power saving mode when you are watching movies on your favourite video player.

==>Overlay Icons
It is an ultra cool extension that shows the application icons over the windows in the Activities window switcher(After installation press Windows key).