OpenOffice.org version 2.1 was released a few days ago. You can find the Release Notes here. This Open Source office suite includes a word processor, spreadsheet, presentation manager, database, and drawing program.

It uses the OpenDocument XML file format as its default file format. However, it can read and write Office 2003 or older Microsoft Office files. I'm guessing that it cannot (yet) read the new Office 2007 file format.

Note that if you plan to run it under Mac OS X, you need to install X11 (provided by Apple on the DVD that came with your Mac) first.