I never leveled a tanking class past 40, but I found the following sources of information extremely helpful.
Fortificat ions is a great resource. Reading this post totally changed my game. Ciderhelm seems to keep it updated.
http://www.tankhard.com/
http://www.tankspot.com/
These are a couple sites that warriors like to use.
http://druid.wikispaces.com/TankSimu lator
