Open the terminal and run the following commands
sudo add-apt-repository ppa:gnome3-team/gnome3
sudo apt-get update
sudo apt-get dist-upgrade
sudo apt-get install gnome-shell
For ubuntu 10.10 users
Open the terminal and run the following commands
Note:- This PPA works but it is outdated
sudo add-apt-repository ppa:ubuntu-desktop/gnome3-builds
sudo apt-get update
sudo apt-get install gnome3-session
After completing the installation Log out and back in, selecting the GNOME Session in GDM
Remove Gnome3 from ubuntu 11.04
Open the terminal and run the following commands
sudo apt-get install ppa-purge
sudo ppa-purge ppa:gnome3-team/gnome3