NeoOffice
NeoOffice is a free open source office suit for OS X. It is based upon the OpenOffice.org suite, but unlike OOo, NeoOffice runs natively on OS X without the need for X11 to be installed. NeoOffice includes a word processing app (very similar to MS Word 2003), a spreadsheet app (very similar to Excel 2003), a presentation app (very similar to PowerPoint 2003), and a drawing app. So, if you want a free office suite that runs natively in OS X, supports a wide variety of file formats including the .odf and even MS Office files, NeoOffice is for you.
Bean
Bean is a light-weight word processor. It is still in beta, so it may have some bugs and be unstable. So, if you're just doing the casual word processing, you might want to consider giving Bean a try.