The Wyrmrest Accord offers three pieces of gear that are veritable must haves for a tank. A cloak at Honored, and a chestpiece and boots at Revered. I have the cloak and am working now on earning those other two peices. If you wish to go all the way to Exalted with them, you are allowed to purchase a wonderful Red Drake to carry you high over the snows of Northrend. Do keep in mind that it requires 300 riding skill, though, something I'm actually still working on.
The Argent Crusade offers some great pants at Honored (pants I earned just yesterday). They even have a red socket, which was especially wonderful as it allowed me to activate the meta gem in my new goggles I crafted for myself yesterday (I'm very proud of them. I shouldn't have to replace them until we really get into raiding). At Revered, they offer a nice head enchant for tanks, so I'm looking forward to that as well. Unfortunately they don't offer anything for a warrior at Exalted (unless you're a tailor, I guess), so I'll probably stop at Revered for now.
The Sons of Hodir offer shoulder enchants at Honored, mammoth mounts at Revered, and even better, improved shoulder enchants at Revered (along with 3-person, improved mammoth mounts). I'll be working on this reputation grind last, although I'm looking forward to the enchants.
I mentioned my goggles and such earlier, and yes, I'm finally uncrittable, even for raiding (540+ defense). That said, of course, I don't think I could just jump into the first 10-man I came across. My health pool still seems very low to me and I want to start stacking some more stamina. Part of it will come from gems, and part of it will come from enchants. Thank goodness our guild has a maxed out enchanter. Although I'm definitely ready to start Heroics, even according to Be.Imba, so I'll be looking for a Heroic Utgarde Keep group here soon. :)