OpenOffice.org is a powerful productivity suite--including tools for word processing, spreadsheets, slideshows and more--with one major additional feature: it's free.
Whether OpenOffice 3--the first version to run natively on OS X and Intel-based Macs--is right for you essentially comes down to this decision: can you live without the latest features in Microsoft Office 2008? Most of the tools you need for productivity are here, minus an e-mail client. There's Writer, a powerful word processor; Calc for spreadsheets; Impress for slideshows; Draw for basic drawing and graphics; and Base to serve as--you guessed it--a database.
OpenOffice 3 is a major upgrade over the previous version, with plenty of new features, native OS support, and all the tools most people would need to get their work done.