i think most of openoffice does not need java. i've run openoffice on linux powerpc without java, i think all you miss out on are some of the wizzards, and the database. however the system requirements for openoffice means that it would never run well on an N800.

powerpoint is a planed format for evince. http://live.gnome.org/Evince/SupportedDocumentFormats

until then, try using openoffice to convert to pdf