Apache OpenOffice: The free, open productivity suite
It is one of the best-known open source applications in this category. It provides tools for word processing, spreadsheets, presentations, graphics and databases. Apache OpenOffice lets you save documents in the OpenDocument format, read Microsoft Word documents and save your work in Microsoft Word format.
It is released under the Apache License, Version 2.0 and can be downloaded and used entirely free of any license fees. The current version, Apache OpenOffice 3.4.1 supports the Microsoft Windows, GNU/Linux and Mac OS X operating systems.
LibreOffice: A powerful open source productivity suite
Developed by the Document Foundation, the LibreOffice application is just for name open Source mean the source code is the same, but the software has gone in a different development direction. (LibreOffice was created in 2010 by OpenOffice developers worried about what Oracle, which had acquired Sun Microsystems, the original developers of OpenOffice.org, would do with the code base.)
It has the same six applications as Apache OpenOffice-Writer, Calc, Impress, Draw, Base and Math-but the two suites differ in terms of applications. It is licensed under the GNU Lesser General Public License (LGPL) 3.0. The current version of LibreOffice, v3.5.6, supports Windows, Macintosh and GNU/Linux systems.
NeoOffice: Office applications for Mac OS X
It is an also just for name open source. It was created before OpenOffice and LibreOffice supported Mac OS. It has all of the features found in OpenOffice.org but, in focusing on the unique needs of Mac users, offers a Mac-like installation process and better support for Mac features, including integration into the OS X interface and use of Mac OS X fonts and printing services.
Google Docs: Create, share and collaborate online
It is an office productivity application that lets anyone with a Google account create, share and collaborate on the Web. Google offers tools for documents, spreadsheets, presentations, drawings and forms, all centrally stored and accessed via the cloud-based storage service Google Drive.
Google Docs integrates with a number of other Google services, Like Gmail, GChat, Google+, Google Calendar and Google Drive, and can be accessed from any device with a browser and Internet connection.
KOffice: The integrated office suite
It offers the three main tools of any office Application: a word processor, a spreadsheet and a presentation application.