Vote for bug 114376
to get native OOo view support in Firefox.
Meanwhile you can use following crude bookmarklet to achieve the same.
Bookmarklet ==>> VU OOo
Function : covert OOo documents *.odt, *.ods, *.odp, *.swx, *.swc, *.swi etc to a viewable *.html
1. copy above bookmarklet to you tool bar
2. now go to http://www.openoffice.org/
3. copy url http://www.openoffice.org/nonav/issues/showattachment.cgi/22319/OOo_2.0_feature_guide.odt (as link)
4. run bookmarklet View OOo
5. on prompt paste url http://www.openoffice.org/nonav/issues/showattachment.cgi/22319/OOo_2.0_feature_guide.odt
You can also test this with other OOo formats
1. sxw file - http://specs.openoffice.org/writer/compatibility/tables_vertical_text_direction.sxw (as link)
2. ods file - http://wiki.services.openoffice.org/mwiki/images/7/78/Xml-load-compare.ods (as link)
3. odp file - http://marketing.openoffice.org/2.0/ooo2prodintroen.odp (as link)