theres this offline wikipedia for the iphone at

people say it works very well and fast
the only thing is, its only for mac's only, and you need to compile a file or something.

taken from site

"If you’re not using Mac OS X:
You need to compile the “indexarticles.cpp”. If your c++ tool chain (using gcc) is working from the command line simply enter “make indexarticles”. I will check if the source happily compiles using Visual C++ on Windows also. If not it should be easy to fix. No rocket science technology used. I promise. But probably you will get into trouble when it comes to use perl and grep. As soon as I find the time I will do a stand alone application for indexing."

my question: ANY windows users out there, can someone compile the file and upload it so the rest of us windows users can use it? I would do it but i have no clue how to, and what compiling means.. lol