GNU TeXmacs is a free wysiwyw (what you see is what you want) editing platform with special features for scientists. The software aims to provide a unified and user friendly framework for editing structured documents with different types of content: text, mathematics, graphics, interactive content. TeXmacs can also be used as an interface to many external systems for computer algebra, numerical analysis, and statistics. New presentation styles can be written by the user and new features can be added to the editor using Scheme.
KOffice is an integrated office suite based on the KDE libraries. KOffice currently includes KWord, KSpread, KPresenter, KChart, Karbon14, Krita, Kexi, KFormula, Kugar, and Kivio. There are no special mail and news clients included in KOffice, because there are KMail and KNode available for KDE anyway. All KOffice components work together, and you can embed every KOffice component into any other KOffice component. This is realized using the KParts object model.
Siag Office is a free office package which consists of the spreadsheet Siag, the word processor PW, the animation program Egon, the text editor XedPlus, the file manager Xfiler and the previewer Gvu. Siag is easy to use, yet infinitely flexible through multiple embedded interpreters and a plugin mechanism that allows other programs to run inside the main document. The supported interpreters are SIOD, Guile, Tcl, and Python.