Unity does not bring in Ubuntu 11.04 an applet to show the desktop in the launcher, if instead there is a keyboard shortcut to access the desktop quickly which is the key combination Super + D.
But, you may be used to going to your desktop by clicking on an icon, so in WebUpd8 they have made a little script, which does the same job as the gnome show desktop applet.
First we install wmctrl by typing in a terminal
sudo apt-get install wmctrl
Then we download the script and the .desktop file, extract and copy the "showdesktop" script in the folder / usr / local / bin using these commands (one by one)
cd wget http://webupd8.googlecode.com/files/showdesktop.tar.gz tar -xvf showdesktop.tar.gz && rm showdesktop.tar.gz sudo mv showdesktop / usr / local / bin /
Now in your personal folder you will have a file «showdesktop.desktop»You can leave it there or move it wherever you want, you just have to drag and drop in the Unity launcher and you will have your icon to show the desktop.
P.S. I suggest you try the keyboard shortcut, it's much faster and you don't have to take your hands off the keyboard at all 