The goal of this guide is to make efficient use of all sources of reputation for outland factions.
Please note that, where applicable, heroic instances should also give rep with the appropriate faction, all the way to exalted.
The most difficult portion of this guide is gaining honored with Honor Hold or Thrallmar. As one hits 58-60, you can't do quests for those factions until you hit honored, so leveling becomes painful. However, once honored is achieved, you can "chain" together your rep gains - start farming the next faction's low level instance for rep while you complete quests for the previous faction.
Outlands Rep
Honor Hold
-Honored: Ramparts, Blood Furnace
-Exalted: Quests, Shattered Halls
Thrallmar
-Honored: Ramparts, Blood Furnace
-Exalted: Quests, Shattered Halls
Cenarion Expedition
-Honored: Unidentified Plant Parts, Slave Pens, Underbog
-Exalted: Steamvault, Quests, Coilfang Armaments, Uncatalogued Species*
*Uncatalogued Species may randomly come from Unidentified Plant Parts turn-ins
Consortium
-Friendly: Mana Tombs, More Crystal Fragments, More Heads Full of Ivory
-Honored: Mana Tombs
-Exalted: Quests, Another Heap of Ethereals, More Obsidian Warbeads, Ethereum Prisoner Keys
Lower City
-Honored: Auchenai Crypts, Sethekk Halls, More Feathers
-Exalted: Quests, Shadow Labyrinth
Scryers
-Honored: Firewing Signets
-Exalted: Arcane tomes, Sunfury Signets, Quests
Aldor
-Honored: Marks of Kil'Jaeden
-Exalted: Marks of Sargeras, Fel Armaments, Quests
Sha'tar
-Honored: Aldor/Scryers turnins
-Exalted: Quests, Tempest Keep
Sporeggar
-Friendly: The Sporelings Plight, Bog Lord Tendrils
-Revered: Kill Bog Lords of any variety
-Exalted: Quests, Bring Me Another Shrubbery, Now That We're Still Friends, More Fertile spores
Keepers of Time
-Exalted: Quests*, Old Hillsbrad, Black Morass
*Note that their quests are worth approximately 13k rep in all
Scale of the Sands
-Friendly: The Vials of Eternity quest
-Exalted: CoT: Battle of Mount Hyjal
Netherwing
-Neutral: Quest line (starts with "Kindness" in Shadowmoon Valley)
-> Must have 300 Riding Skill to continue <-
-Friendly: A Slow Death, Netherdust Pollen, Netherwing Crystal, Not So Friendly Skies, Great Netherwing Egg Hunt (non-daily)
-Honored: Booterang: A Cure for the Common Worthless Peon, Picking up the Pieces, Dragons Are the Least of Our Problems
-Revered: Disrupting the Twilight Portal, Non-repeatable quests
-Exalted: The Greatest Trap Ever Laid
Note: Unless otherwise noted, quests are "daily" quests, and can only be COMPLETED once per day (though in some cases, drops may be gathered but not handed in). Any of the daily quests from the previous tier can still be completed at higher rep levels - e.g. Once you're revered, you can do The Greatest Trap Ever Laid AND Not So Friendly Skies, each once daily.
Information courtesy "Joni of Malygos" - http://forums.worldofwarcraft.com/thread.html?topicId=96053497&sid=1
Kurenai
-Exalted: Mobs, quests, Obsidian Warbead turn-ins*
Mag'har
-Exalted: Mobs, quests, Obsidian Warbead turn-ins*
*Note that Consortium also takes warbeads, so it is "wasteful" to turn them in here until you are exalted with Consortium.
The Violet Eye
-Exalted: Karazhan, quests
Ashtongue Deathsworn
-Exalted: Black Temple
Ogri'la
-Neutral: Quest chain "Speak with the Ogre"
-Honored: The Relic's Emanation (Daily), Wrangle Some Aether Rays, Bombing Run
-Exalted: All 3 above, plus Banish the Demons
Sha'tari Skyguard
Exalted: World of Shadows, Fires Over Skettis, Escape from Skettis, Wrangle Some Aether Rays!, Bombing Run
"Quests" refer to one-time quests. By "efficiency," basically the goal is to make use of every resource, meaning if a certain quest, repeatable turn in, or mob kill will eventually stop giving rep, it is better to do that first. Is it faster at level 70 to do things this way? Possibly not. But, as one is leveling, the options available generally open up in the order listed, so by following this guide, one will have the highest rep possible upon reaching 70, making the 70 grind to exalted that much shorter.