OpenOffice is a software suite that works great on Windows and Linux machines. I like it as a free alternative to Microsoft Office, which can easily run into hundreds of dollars per person. From the OpenOffice.org web site:
OpenOffice.org 3 is the leading open-source office software suite for word processing, spreadsheets, presentations, graphics, databases and more. It is available in many languages and works on all common computers. It stores all your data in an international open standard format and can also read and write files from other common office software packages. It can be downloaded and used completely free of charge for any purpose.