OpenOffice.org

"OpenOffice.org 2 contains all the office software you need, in one single package. You don't have to worry which version to install: one installation program provides everything. The installation also includes features which some expensive rivals do not - for example, the ability to create .pdf files when you want to guarantee what the recipient sees on their computer. There is also a growing range of extensions: additional features that any developer can provide. OpenOffice.org releases release software several times a year so you can take advantage of new features as quickly as possible."

-OpenOffice.org

OpenOffice.org is a great free alternative to Microsoft Office and is available on multiple platforms. OpenOffice.org includes features that are very similar to Microsoft Office, such as a full word processor (Writer), a spreadsheet application (Calc), and presentation software (Impress).