Open Office 3 – Beta is a free open source Intel only Mac alternative to Microsoft Office. I’ve had good luck so far. Give it a try if you have a newer Mac with an Intel processor.
Update:
Try out NeoOffice as well. It is based on OpenOffice but Sun Microsystems has made it work on PPC as well as Intel machines. It is free but they kindly accept donations if you are pleased with the software. It seems to work great. I’ve yet to have a problem on both PPC and intel Macs. I’m so close to erasing Office on my machines ;0) Yaaaaaaay!!