If Word crashes and then restarts, don't accept its recovered document. Close it and then open the last version you saved. Also I only ever use Save As now, not File » Save, or Command-S. I think it's this form of saving that's causing the problems. Maybe the disastrous bug is part of a 'quick save' routine?
Finally, if there's a document that Word crashes with, and continues to crash with, I had some luck opening it on a Windows version of Word using VMWare Fusion, and then saving it out again. This seems to iron out the bugs, but it didn't always work (and in fact, worked fewer times than it actually worked in the first place).
[robg adds: I haven't experienced many crashes with Word 2008, but my document needs for it are quite light by comparison, so perhaps it has something to do with the size and complexity of the document in question.]

