Abiword -
http://www.abiword.com/ - is a serious cross-platform wordprocessor with some heavyweight abilities. In some ways I prefer it to OOo Writer. It can import and export OpenDocument files, but is more aimed at cross-platformability and Word (.doc) use.
"Presently, AbiWord can open most Microsoft Word documents well. However, if the document has complicated tables, text boxes, embedded spreadsheets, and so forth, then it might not work as expected. Developing good MS Word filters is a very difficult process, so please bear with us as we work on getting Word documents to open correctly. If you have a Word document which fails to load, please open a Bug and include the document so we can improve the importer.
Saving as .doc - AbiWord can currently save in an MS Word compatible ".doc" format. This is done by saving as Rich Text Format (.rtf) but with a .doc extension. The file extension does not mean that the file is a binary Microsoft Word document and .doc may contain RTF, HTML or plain text. This is a feature — Microsoft themselves have used .doc to exploit a mis-feature of MS-Word.
Some developers and even a few users have suggested that this is dishonest and 'cheating'. In fact this 'cheating' is something Microsoft themselves have done in their own software! (Example: MS Wordpad on Windows 98 claims to save as Microsoft Word 6.0 (.doc) but if you look at the files in a text editor you can see that it is in fact Rich Text Format). There are no plans to support binary MS Word export."
I like Abiword a lot, but I think that OpenOffice have the right idea going with the OASIS OpenDocument format - I'm pretty sure that's where we'll mostly be in 2010 (and thank goodness for that!).