OpenOffice (formally known as OpenOffice.org) is an open-source program used as an alternative to Microsoft Office.  It is free to download, and does not require the user to register.  The software is available on both PC and Mac.  OpenOffice.org Writer is the equivalent of Microsoft Word, but it features other programs as well, including OpenOffice.org Impress, which can be used to create and run Powerpoint files.

The main advantage of OpenOffice.org is its ease of use.  It loads very quickly, and will automatically save your work as you type, preventing a loss of work in case of a sudden shutdown.  The software is constantly and automatically updating to fix bugs and add new features, but it never becomes complex to use.  OpenOffice Writer works with established file extensions like .doc, and can easily save and convert files.  However, its standard extension is .odt, and since it is not have widespread usage, you will need to convert your documents to .doc if you want to share them with others.

Naturally, the website is http://www.openoffice.org