LibreOffice is a productivity suite that is compatible with other major office suites, and available on a variety of platforms. It is free software and therefore free to download, use and distribute.

Hours ago, the PPA for LibreOffice created to make installation easy for Ubuntu user.
The PPA provides packages for Ubuntu Lucid, Maverick, and Natty, use following commands to start installation

sudo add-apt-repository ppa:libreoffice/ppa

sudo apt-get update

sudo apt-get install libreoffice

After installation, launch at Applications -> Office menu.

To read more about LibreOffice, refers to