This simple program displays the text-only Wikipedia compressed dumps, currently available at http://download.wikimedia.org/backup-index.html, generally named like pages-articles.xml.bz2.

It's fairly useable now for wikipedia reading, altough lots of rendering or layout glitch occurs.
It is focused on usability, and not necessarily trying to mimic the online web interface.

Features includes a Qt viewer with basic text mark-up, following links, ability to read directly on the .bz2 compressed file (although some index creations step is needed on first run), tab-like list of articles with load-in-the-background by default, a simple but useful keyword search, very light source-code, optional latex rendering, no install necessary.