http://www.diplom.org/Online/variants/1900-GG.pdf
Created by B. M. Powell and known on this site as Von Powell, the Gamer's Guide to 1900 is the go to source for information on changes made in 1900 to create a better game.
The guide covers every single Great Power, including changes made to them and how to deal with these changes.
There is also information on Switzerland, and an extremely well done AAR on an example game with a Russian victory.
Enjoy!