There's a nice post at Web Worker Daily listing ten free alternatives to Microsoft Word. The comments point to a few more.
Having switched over to Macintosh and OS X, I've been delighted by TextEdit (which comes with a Mac), Bean (a free download), and Pages (part of iWork, not free). I've listed these applications in order of increasingly complexity: Pages is the choice if, for instance, you need to create columns. I'm also very happy with Smultron, a free text-editor with tabs. And I'm even happier to be working on a computer without Microsoft Word.
10 Free Minimalist Word Processors for Greater Productivity (Web Worker Daily)
My version of Amish computing