Pocket Wikipedia is a hand-checked selection from Wikipedia made by Schools Wikipedia which is about the size of a fifteen volume encyclopaedia (24,000 images and 14 million words). The application is a freeware software and works on Windows, Linux and Windows Mobile version.
However, the oiginal Windows Mobile version is limited. The UI is outdated (it was meant for Windows Mobile 2003) and does not support Smartphone. As I am using both a PocketPC and Smartphone, my aim is to improve the application so that it can run on both devices.
Note: Due to the large file size, the binary does not include the database (Wikipedia.wi). You will need to download the original application and install it. When the modified application asks for the database location, specify the path to where you install the original application.
UPDATED (24 June 2010): I have also created a MobiPocket Reader (.PRC) version of Wikipedia, see this post