While you won't find a Mac version of OpenOffice.org, NeoOffice/J is based on the OpenOffice.org suite. NeoOffice/J does a pretty good job of opening Microsoft Word documents with medium formatting complexity. Menus and toolbars are pretty similar to those in Word for Mac (see Figure 2), with a few small exceptions; for example, word count is buried on the Statistics page (File > Preferences > Statistics).
Figure 2 NeoOffice/J offers a familiar look and feel for Office users.
NeoOffice/J will also open documents created in a number of other formats, including HTML, StarWriter, and WordPerfect. On the file export side, NeoOffice/J supports writing directly to PDF files, something you can't do directly from Word for Mac.
Although NeoOffice/J doesn't recognize macros written in Visual Basic, it does have the same macro recording and editing facility as in Word for Mac and uses a BASIC syntax for the macro language. You could convert simple macros, but anything beyond that and you might as well start from scratch.
AbiWord is another freebee alternative, available for OS X 10.2 and higher. A few complaints right off the bat have mostly to do with appearance issues, such as chopping off the Courier font on the letter y and others with descenders, and poor rendering of the red squiggly line under misspelled words or the blue underline for hypertext links.
AbiWord doesn't have a standalone help system but does have direct links to the AbiWord web site. You also won't find a macro recording or playing facility, as in Word for Mac or NeoOffice/J.