What's the best Pre-raid tanking warrior gear outside the first raids at 70? I'm looking to gear my tanking warrior with as much blue's AND purples outside raids.

Getting geared up for raiding can get a bit boring but well worth it in the end if you enjoy tanking. With that said here are the best items, in my opinion, that will help you out the most for starting out in Karazhan. I will also list a few different choices of items for you as well to help tailor to your tanking style and also gives you a bit of variety so if something doesn't drop for you off a boss you have other alternatives to it. On a side note, it also lets me try out the WoWhead item links on my site as well.

Head Slot Items and Enchant
Myrmidon's Headdress - This helm is a quest reward for the quest "The Warlord's Hideout" in Steamvault.
Warhelm of the Bold - This helm drops off the last boss in The Botanica, Warp Splinter.
Felsteel Helm - You can get this helm from any blacksmith that can craft it. You may also find it on the AH cheaper than the cost of the mats to make it.

Glyph of the Defender - Great tanking helm enchant and requires Revered with the Keepers of Time.

Neck Slot Items
Thalodien's Charm - This is a quest reward from the quest "Shutting Down Manaforge Ara" in Netherstorm. It is also important to note that the quest is a Scryer quest so if you are Aldor you might want to check out the other alternatives.
Natasha's Battle Chain - This is the alternative to the above. Not quite as good but a great choice if you are Aldor and can not do the Scryer quest. This is a quest reward for the quest "The Hound-Master" in Blade's Edge Mountains.
Strength of the Untamed - Get this neck from being Revered with Cenarion Expedition.
Maladaar's Blessed Chaplet - This one drops off Exarch Maladaar in Auchenai Crypts but only in heroic mode.

Shoulder Slot Items and Enchants
Shoulderguards of the Bold - This shoulder drops off Murmur in Shadow Labs.
Fanblade Pauldrons - Drops off Shirrak the Dead Watcher in Auchenai Crypts in heroic mode.

Greater Inscription of the Knight - Enchant requires Exalted with Scryer.
Greater Inscription of Warding - Enchant requires Exalted with Aldor.

Back Slot Items and Enchants
Devilshark Cape - Drops off Warlord Kalithresh, which is the last boss in Steamvaults.

Enchant Cloak - Greater Agility - Good enchant that gives +12 Agility
Enchant Cloak - Dodge - Good enchant that gives +12 Dodge

Chest Slot Items and Enchants
Jade-Skull Breastplate - Drops off Nethermancer Sepethrea in The Mechanar.
Vindicator's Hauberk - Requires Revered with the Aldor.
Breastplate of the Bold - Drops off Harbinger Skyriss in The Arcatraz.

Enchant Chest - Exceptional Health - Enchant gives +150 health
Enchant Chest - Exceptional Stats - Enchant gives +6 to all stats

Bracer Slot Items and Enchants
Vambraces of Daring - Drops off the last boss in Hellfire Ramparts only in heroic mode.
Sha'tari Wrought Armguards - Quest reward from the quest "The Soul Devices" in Shadow Labs.

Enchant Bracer - Fortitude - Enchant gives +12 Stamina

Hand Slot Items and Enchants
Thatia's Self-Correcting Gauntlets - This drops off Dalliah the Doomsayer in Arcatraz.
Gauntlets of the Chosen - Requires Revered with the Scryers.
Gauntlets of the Bold - Drops off Warlord Kalithresh in Steamvault.
Felsteel Gloves - Yet another piece of the Felsteel set which is crafted by Blacksmiths. Also may find this on the AH.

Enchant Gloves - Major Strength - Gives +15 Strength
Enchant Gloves - Threat - Gives an additional 2% threat

Waist Slot Items
Sha'tari Vindicator's Waistguard - Reward from the quest "How to Break Into the Arcatraz".
Lion's Heart Girdle - Drops off last boss in Hellfire Ramparts only in heroic mode.
Girdle of the Immovable - Drops off Quagmirran in Slave Pens only in heroic mode.

Leg Slot Items and Enchants
Timewarden's Leggings - Requires Revered with Keepers of Time.
Greaves of the Shatterer - Drops off Warchief Kargath Bladefist in Shattered Halls.
Felsteel Leggings - Third and last piece of the Felsteel set which is made by Blacksmiths and can also be found on the AH.

Nethercleft Leg Armor - Best leg enchant for prot warriors.

Feet Slot Items and Enchants
Boots of the Colossus - Drops off Pandemonius in Mana-Tombs but only in heroic mode.

Enchant Boots - Fortitude

Finger Slot Items
Elementium Band of the Sentry - Drops off Harbinger Skyriss in Arcatraz.
Violet Signet - Requires Friendly with the Violet Eye. You can obtain Friendly just by doing the attunement quests for the Karazhan key. (You can read more on this by checking out my guide How To Get Keyed For Karazhan.)

Trinket Slot Items
Gnomeregan Auto-Blocker 600 - You can purchase this from the badge vendor in the middle of Shattrath City.
Adamantine Figurine - Drops off Blackheart the Inciter in Shadow Labs.

Weapon Slot Items
The Sun Eater - Drops off Pathaleon the Calculator in Heroic Mechanar.
Grom'tor's Charge - Not nearly as good as the Sun Eater but still viable. Reward from the quest "The Cipher of Damnation" in Shadowmoon Valley.

As for enchants, we all know Executioner or Mongoose is the way to go but at this point the mats may be hard to come by and these enchants are fairly expensive. For these weapons listed above you might want to try out Potency or even Greater Agility.

Shield Slot Items and Enchants
Crest of the Sha'tar - Requires Exalted with The Sha'tar.
Ogri'la Aegis - Requires Revered with Ogri'la.
Aegis of the Sunbird - Drops off High Botanist Freywinn in The Botanica.

Enchant Shield - Major Stamina - Gives +18 Stamina.

Ranged Slot Items
Gyro-Balanced Khorium Destroyer - This is a craftable item with engineering. Usually can find a lot of these on the AH but are typically a bit expensive. Wouldn't be too difficult to farm out the mats for this yourself instead of buying it off the AH.

That wraps this up. Please also note that I haven't included many badge items as well. Also it's good to note this doesn't include new items that came out with patch 2.4 (happened that way since I started this weeks before the new patch came out but just now got finished writing it up). I will update this over time and will add the new items in as soon as I get some time but I feel this is a great place to start.