Clean, modern and airy... the new Elementary Theme is available and easy to install for Ubuntu 11.10 and 12.04 users.
You'll need to open a terminal window to run the commands. Do one line at a time and press ENTER.
Install the theme:
tar -xzvf elementary.tar.gz -C ~/.themes
Now you need to install the Gnome Tweak Tool with the following command:
sudo apt-get install gnome-tweak-tool
It is about 25mb. Once installed, go to the dash and search for "Advanced Settings" and open it. Click on the Theme menu and change both GTK+ and Window Themes to "Elementary". You may need to logout and log back in for full changes to take effect.
Get the cloud wallpaper here: