Wikipedia on the iPhone

Patick Collison spent the Christmas break to code an iPhone application which allows the full Wikipedia project (including the app itself, indexes and dumps) to be stored and viewed offline on 2GB of the iPhone’s free space..
There’s also a mongrel-based ruby server for offline browsing on a PC used for debugging during the development. See sh/server in the source distribution.
As he admits this is a work in progress so theres still some problems opening certain articles and its prone to crashing..BUT its working AND hes working on improving it.

Wikipedia iPhone

Installation
Put the app in /Applications. Use something like Customize.app to get it onto your springboard. Untar the dump, and put the contents at /var/root/wp. If using Windows, check out the in-depth Windows installation instructions contributed by rebelxtnut.

Application: Wikipedia.zip

Dump: English (October 2007) German (January 2008)