Just found this in Wikipedia and search on Google: there is a new Firefox extension called ODFReader:

http://www.alcoholicsunanimous.com/odfreader/
https://addons.mozilla.org/extensions/morei...firefox&id=1888

The extension is still very early in development and needs more effort to further its progress.

It will go a long way to help the spread of ODF if everybody can read it without downloading the 70-100MB+ OpenOffice.org main program (at least on Windows or Mac), when a 20-200kb+ Firefox extension can do the job.

Also check out this entry at OpenOffice.org Wiki
http://wiki.services.openoffice.org/wiki/Firefox_ODFReader_extension