I know not everyone levels Fury so I'm going ahead and making another post, much like my previous one, as to how an Arms spec will still do for tanking up until 70.
5/5 Deflection - +5% to parry? Yes pls.
5/5 Iron Will - +15% chance to resist Stun and Charm effects is situational but still helps. I normally skipped this unless I was speccing for PVP but I suppose it could help while tanking.
3/3 Improved Thunder Clap - +100% more damage for Thunder Clap which also causes more threat from Defensive Stance. Not too shabby if you'll be tanking a lot but you wont really use this soloing. If you have it, great, if not, oh well.
1/1 Anger Management - 1 rage per 3 seconds as long as you're in combat. Worth the 1 point.
3/3 Deep Wounds - All melee crits cause your enemy to bleed 60% of your weapons average damage over 12 seconds. Bleed effects are great because they ignore armor and will keep consistant threat on the mob.
5/5 Weapon Specialization - Whichever weapon you specced in to, thats what you want to use while tanking. I prefer sword spec for the additional swing but +5% chance to crit with the others arent bad at all.
2/2 Blood Frenzy - Anytime Rend or the Deep Wounds debuff is on the target they will take an additional 4% physical damage from all sources. More damage = more rage.
1/1 Endless Rage - The amount of rage you obtain from damage delt is increased by 25%.
In my opinion, Arms doesn't offer as much in the ways of tanking as a Fury build does because some of the talents arent taken by players while leveling. Most of the great stuff in the Fury tree is viable while soloing unlike, say, Iron Will or Improved Thunder Clap. Arms also loses one of its best attacks in Mortal Strike since it cannot be used in Defensive Stance.
Either way you spec you'll still be a viable tank as long as you use Sunder Armor, use Revenge whenever it's available and pop Shield Block every cooldown on hard hitting mobs. The rest depends on your healer.
My advice is to warn your group ahead of time that you are not Protection and that you'll require a little extra time to grab aggro before they start to DPS. You shouldn't take much more damage early on in Outlands instances since you'll still be using a shield, it's just your ability to solidify aggro that seperates us. We don't have Devastate, Improved Revenge, Improved Shield Block or Last Stand but we can still hold our own with a patient group and a competent healer.