http://www.OpenOffice.org The home of the open source productivity suite. Extended documentation, a knowledge base, and links to the various mailing lists that keep this project running.
http://wwws.sun.com/software/star/staroffice/ OpenOffice.org's commercial big brother, produced and marketed by Sun Microsystems. This version includes a database and a few other closed-source widgets and tools.
http://www.taming-openoffice-org.com/ Aimed at the person who wants to get more out of OOo. Contains many valuable tips, links, and pointers to other books that cover OOo in depth.
http://www.KOffice.org The KDE Office Suite home. Downloads, news, mailing lists and archives.
http://www.gnome.org/gnome-office The umbrella home for the GO Suite.