Here's a guide to getting gear for a main tank, as he holds a very important position, before you head off to Karazhan to kill those big bad raid bosses!
I don't think any of these require a raid to get.
Chest: Hit rating is important for tanks too!
Forge Camp: Annihilated - Quests - World of Warcraft
Helm:
Myrmidon's Headdress - Items - World of Warcraft or Felsteel Helm - Items - World of Warcraft
Legs:
Legguards of the Resolute Defender - Items - World of Warcraft
Belt: Also gets you the key to Arc...
Sha'tari Vindicator's Waistguard - Items - World of Warcraft
Back: Crafted but not that bad at all
Cloak of Eternity - Items - World of Warcraft
Bracers:
Sha'tari Wrought Armguards - Items - World of Warcraft
Shoulders: This sucks these are a drop item from SLabs but there is no other option excepting pvp gear.
Shoulderguards of the Bold - Items - World of Warcraft
Feet: Greens but get over it they are actually pretty nice. There's a comment on wowhead about needing an epic flying mount, as its part of the "netherwing" quest chain.
Ascendant's Boots - Items - World of Warcraft
Otherwise for feet, from heroic mana tombs:
Boots of the Colossus - Items - World of Warcraft
Ring: This one is kinda tough for me.
Protector's Mark of the Redemption - Items - World of Warcraft
Ring: Another Green, but this ring is OP for a green.
Wind Trader's Band - Items - World of Warcraft
Neck:
Maimfist's Choker - Items - World of Warcraft or Mark of the Ravenguard - Items - World of Warcraft) or Thalodien's Charm - Items - World of Warcraft (scryer quest)
Trinket:
Dabiri's Enigma - Items - World of Warcraft
Trinket2:
Adamantine Figurine - Items - World of Warcraft
Weapon: There are two blues from this quest chain but its quite long.
Grom'tor's Charge - Items - World of Warcraft
and Last but not least your Shield. I only listed one other item that is from a drop and unfortunatly there's no easy way to get a shield. Reason number one for this choice is its the best there is from normal 5mans and reason number two is the faction that you get rep w/:
Aegis of the Sunbird - Items - World of Warcraft and that rep goes towards being able to buy: Crest of the Sha'tar - Items - World of Warcraft Hopefully while your going for the Shoulders you can get Platinum Shield of the Valorous - Items - World of Warcraft as well. The other option is after doing Dailies for a while pick up Ogri'la Aegis - Items - World of Warcraft
Otherwise, merciless gladiator's shield wall is your best bet for a shield.
These are just (fairly) easy to get. I haven't included enchantments or gems cuz you can decide that for yourself depending on what stats you need. If you have any that are better and easier to get, I'll replace my picks with yours. Get to tanking!