LibreOffice is GPL-licensed free and open source office suite , with Writer, Impress, Calc spreadsheet, Base relational database frontend
Install using sudo apt-get install libreoffice-kde
Open Office was installed by default in older versions of (K)Ubuntu. It has been replaced by LibreOffice (which is similar) and is no longer available in (K)Ubuntu.
KOffice suite is part of the KDE project and provides capabilities of OpenOffice suite without the licensing restrictions of OpenOffice. It can be used in any version of (K)Ubuntu. Install using: sudo apt-get install koffice
AbiWord is a fast, collaboration-enabled word processor. For the most current version see the AbiWord web site. For install from repositories: sudo apt-get install abiword
GoldenDict is multi-lingual dictionary and translator that supports Babylon and StarDict translation dictionary files and has multiple modular plugins. Install using: sudo apt-get install goldendict
Xournal is a free (GPL-licensed) GTK/Gnome-based application for notetaking, sketching, or keeping a journal using a stylus. Install using( Remember: universe repositories must be enabled): sudo apt-get install xournal