Open Office Extensions
(This blog was written for versions of OpenOffice up to Version 3.4.0)
Like Firefox, OpenOffice also comes with extensions that can be used to improve its functionality. The site - http://extensions.services.openoffice.org/application - lists Extensions.
At this page it is possible to view All Extensions or view them as applicable to the various Applications in Open Office (eg Writer, Base, Calc, Draw etc) or by the Highest Rated, Most Popular, Most Recent etc.
People all over the world create these extensions and then provide them for all users of Open Office so it is not uncommon to find extensions that are in a foreign language.
The site includes instructions on installation of extensions as does the Help Files in the Open Office applications.