I'm thinking Calligra's focus on comprehensiveness makes it especially worth checking out. Here are some of the highlights of what it includes.

Imports Native File Formats

Among Calligra's Office applications are a word processor, a visual database creator, and modules for spreadsheets, presentations, diagrams and flowcharts, and note taking.

Graphics applications, meanwhile, include components for drawing and for vector graphics, and there's a project management app as well.

Mobile versions of Calligra feature user interfaces optimized for touch computing. In this first release, there's one such version for the Nokia N900 smartphone that includes both a viewer and a document editor with support for text documents, spreadsheets, and presentations. A second version is integrated into the tablet environment used by KDE, but it currently supports only viewing.