If you haven't downloaded OpenOffice.org 3 yet, you may be missing something. Since OpenOffice.org 3 was released a year ago, it has been downloaded some 100 million times.
OpenOffice is a suite of software packages that includes a program "Writer" for writing text documents, similar to Microsoft Word, a program "Impress" for writing and performing presentations, similar to Microsoft PowerPoint, a spreadsheet program "Calc", similar to Microsoft Excel, and a database program "Base", which is similar to Microsoft Access.
Unlike Microsoft Office programs, OpenOffice.org software is free and open source. Previously it belonged to Sun Microsystems and now to Oracle, since Oracle has acquired Sun. However, Oracle stated that they plan to continue to support OpenOffice.org as open source project.