With all the fuss about the iPad I thought I'd look up the electronic document format it's supporting. Looks like the iPad supports the ePub format.
I found this presentation on SlideShare that explains the format but if you're in a hurry, go straight to these downloads :)
Aspose.Words is a plugging for Microsoft Word to allow save to ePub format
Calibre is a ePub converter/reader but only takes input from .txt files.