OpenOffice

OpenOffice is a free document processing suite available at http://www.OpenOffice.org

It utilizes the Open Document format, which is an open standard, but can also read and write proprietary formats, such as Word for Windows, Portable Document Format (PDF -- "Acrobat") and many others.

It has word processor, spreadsheet, database, and presentation (like Power Point) integrated into a convenient (and free) package. This software runs on all platforms, including Linux.