The following links should be useful if you're looking for more information about KDE or Calligra.
The Calligra homepage. Here you can find information on how to get and install Calligra, news about Calligra development, screenshots etc.
The KDE Homepage. KDE is the most advanced and absolutely free desktop environment for unix-like operating systems. Calligra makes use of the KDE libraries.
Qt™ page. The creators of the C++-toolkit Qt™. KDE and Calligra make use of Qt™.