Pocket Wikipedia is an excellent freeware application that brings Wikipedia pages to your PC and Windows Mobiles for offline reading. The Pocket Wikipedia comes as a 175 MB zipped file(not even required to install!) that has hand picked pages of Wikipedia with 14 Million words and 24,000 images.
The wide range of topics covered by this freeware are good enough to read when you are on the move. It works on Windows Mobiles, Linux PCs and Windows PCs.