KOffice and ODF

ODF originated within the model of coarse-grained document composition: embedding documents
within documents. KOffice2 is using ODF to store documents composed of fine-grained objects.
We're bridging the dichotomy between the creative worker and the office worker by having the
full range of  applications and components available. And we're adding object types that have
never before been available to anyone, such as editable musical notation. And color management
across the board. And, but that's only started just now, workflow management using the
integrated project planner.

And as for links:

http://wiki.koffice.org/index.php?title=Architecture
http://dot.kde.org/1168284615/
http://akademy.kde.org/conference/talks/06.php

and of course, most importantly:

http://websvn.kde.org/trunk/koffice