ZIM

ZIM is a file format for storing complete dumps of wikis so that they are usable for offline reading, with the entire contents contained in a single, relatively compact file. It is based on the older Zeno format which is no longer in use.

Format info

 * File format description

Software

 * ZIM readers

Other links

 * Wikipedia article
 * ZIM Wiki
 * The Whole Wikipedia in English with pictures in one 40GB big file