OpenOffice, the free software/open source successor to Sun's Star Office, has shipped for Mac OS X. It's just a developer build, and you need to install XFree86 to get it to run, but it is a free-as-in-speech/free-as-in-beer alternative to MSFT Office. OpenOffice reads and writes Microsoft Office files, including most of the complex ones (you can use OpenOffice to exchange revision-marked documents with Word users, for example).
It's butt-ugly and a pain in the ass to install, but both of those are temporary conditions. The OpenOffice Mac OS X hackers are promising to build an Aqua version of the software for 1.0, which'll increase the ease of installation and the aesthetic pain considerably. Can't wait.
Meantime, Open Office 1.0 is available for most Linuxes and other Unix flavors -- enjoy the freedom! Link Discuss (Thanks, Charlie!)