With the Open Beta Client there's The Warhammer Online Players Guide. It's currently one of the best guides to your WAR experience there is. Included are player career basics, information about the basics of RvR, combat basics, quests and how they work, UI walk through, skills and abilities descriptions exists as well. Check it out!

Warhammer Online Players Guide (Right Click Save As – Requires Adobe Acrobat Reader)

This guide was made earlier during the beta phases, so several things have likely changed since then, it's still a guide that serve as a good foundation, especially for new users.