Do you use spreadsheets? How about a word processor? Do you make presentations?
If you answered "yes" to any of the above questions, you might want to get to know OpenOffice.org.
OpenOffice.org is an open source project with a long and impressive history. It began its life as Star Office, a commercial project undertaken by Sun Microsystems. I believe what happened next was that after years of languishing behind Microsoft's Office suite, Sun decided that they would benefit more by making it open source.
Since then, the project has taken on a life of its own, and like many open source projects, it has flourished. OpenOffice.org runs on most popular platforums, including GNU/Linux, FreeBSD, and Mac OS X. It even runs on Microsoft Windows if you are still stuck using that.
The Mac OS X version has taken some time to operate well, but with the help of the NeoOffice folks, its been on Mac OS X for years now. I believe the core OpenOffice.org 3.0 works fine on Mac OS X intel too!
Wait - I know what you are going to say: "What about file incompatibility with Microsoft Office?"
Are you ready for the answer? You sure? Well here it is: file formats are thankfully not a problem OpenOffice.org, as it can open and save to Microsoft Office file formats. Hopefully the open office file format will take better hold than the proprietary formats which Microsoft has used (or abused, depending on your perspective) to gain market share, which in my opinion are of inferior quality due to their closed nature.
You see, standards are a good thing!