Cenarion Expedition
Description
An exploratory force sent to Outland by the Cenarion Circle to study surviving life forms. The Cenarion Expedition has quickly gained in size and autonomy since the opening of the Dark Portal.More info
Upon the reopening of the Dark Portal to Outland, the Cenarion Circle dispatched an exploratory force, known as the Cenarion Expedition, to explore the uncharted world. Much like the Circle, it is a coalition of night elf and tauren forces. The Expedition maintains its primary base at Cenarion Refuge in Zangarmarsh; it has also made its presence known on Hellfire Peninsula, in Terokkar Forest, and in the Blade's Edge Mountains. Cenarion Refuge is located immediately west of Thornfang Hill.
The Refuge is located in the Zangarmarsh for the primary reason of studying the rich wildlife located there. However, members have discovered problems in the Marsh with the naga. Those heroic enough to fight the naga at Coilfang Reservoir will be well rewarded.
Many players like going back to grind Expedition reputation because of the
Cenarion War Hippogryph mount available at Exalted, as well as being required for the achievement/title 
Guardian of Cenarius. A neat benefit to gaining reputation is that the NPCs will say nicer things to you as you level up!
Kill Naga, while also running The Slave Pens whenever you can; a good instance run will net reputation faster than soloing. Alternatively, the player can begin turning in
Unidentified Plant Parts for a chance at an 
Uncatalogued Species, which can be turned in for 500 reputation. It is suggested that the player save his Uncatalogued Species until after Honored status is achieved, as the quest cannot be continued past that point, while Uncatalogued Species can be used until Exalted.
If you are an herbalist, and interested in Sporeggar reputation, you may want to grind the Bog Lords which can be found in the NE, SE, and SW corners of Zangarmarsh. Their bodies can be "picked" by herbalists and often yield Unidentified Plant Parts, while every kill yields 15 reputation with Sporeggar.Honored to Revered
Once the player is Honored, running Slave Pens and the The Underbog (with the exception of Hungarfen and some giants), will no longer grant reputation. You should now do any Cenarion Expedition quests in Hellfire Peninsula, Zangarmarsh, Terokkar Forest and the Blade's Edge Mountains. It is also the time to turn in any Uncatalogued Species you have found. Doing this should get you part of the way into Revered.
Alternatively, you can finish leveling to 70 and run The Steamvault. Each run gives just over 1500 reputation if you clear all mobs. Also within the Steamvault lies a repeatable quest,
Orders from Lady Vashj, which begins with 
Item #24367. You will then be able to turn in 
Coilfang Armaments, which drop in both Steamvault and Slave Pens, receiving 250 reputation for the first turn-in and 75 reputation each thereafter. This turn-in is available all the way to Exalted. Note: in 4.3 there was an oversight which removed the pre-requisite quest Orders from Lady Vashj. You can still purchase the Armaments on the AH but cannot turn them in.
Once you are 70 and have upgraded your gear, you can opt to run Slave Pens, Underbog, and Steamvault on Heroic Mode. They award significant reputation: regular mobs are worth 15 reputation, 2 for non-elites, and 150/250 for bosses. This method works until Exalted.Revered to Exalted
Continue with the same strategy as above: finish any remaining quests and run Steamvault.
It is also possible to run Slave Pens, Underbog, and Steamvault on Heroic Mode. The reputation gained is not much more than running Steamvault in normal mode, whilst the time investment for heroic dungeons is much higher, possibly resulting in a lower net reputation per hour.
Wrath of the Lich King
In Wrath of the Lich King, a new quest hub was added that grants Cenarion Expedition reputation. Completing the quest related to
D.E.H.T.A's Little P.I.T.A. in Borean Tundra will net you a significant amount of reputation. Like other quests, it's best to complete this hub after Honored. Just remember not to kill an animal and then speak to the NPCs, as they will be hostile for several minutes afterwards.
The Refuge is located in the Zangarmarsh for the primary reason of studying the rich wildlife located there. However, members have discovered problems in the Marsh with the naga. Those heroic enough to fight the naga at Coilfang Reservoir will be well rewarded.
Many players like going back to grind Expedition reputation because of the
Cenarion War Hippogryph mount available at Exalted, as well as being required for the achievement/title Guardian of Cenarius. A neat benefit to gaining reputation is that the NPCs will say nicer things to you as you level up!Reputation
Neutral to HonoredKill Naga, while also running The Slave Pens whenever you can; a good instance run will net reputation faster than soloing. Alternatively, the player can begin turning in
Unidentified Plant Parts for a chance at an Uncatalogued Species, which can be turned in for 500 reputation. It is suggested that the player save his Uncatalogued Species until after Honored status is achieved, as the quest cannot be continued past that point, while Uncatalogued Species can be used until Exalted.If you are an herbalist, and interested in Sporeggar reputation, you may want to grind the Bog Lords which can be found in the NE, SE, and SW corners of Zangarmarsh. Their bodies can be "picked" by herbalists and often yield Unidentified Plant Parts, while every kill yields 15 reputation with Sporeggar.Honored to Revered
Once the player is Honored, running Slave Pens and the The Underbog (with the exception of Hungarfen and some giants), will no longer grant reputation. You should now do any Cenarion Expedition quests in Hellfire Peninsula, Zangarmarsh, Terokkar Forest and the Blade's Edge Mountains. It is also the time to turn in any Uncatalogued Species you have found. Doing this should get you part of the way into Revered.
Alternatively, you can finish leveling to 70 and run The Steamvault. Each run gives just over 1500 reputation if you clear all mobs. Also within the Steamvault lies a repeatable quest,
Orders from Lady Vashj, which begins with Item #24367. You will then be able to turn in Coilfang Armaments, which drop in both Steamvault and Slave Pens, receiving 250 reputation for the first turn-in and 75 reputation each thereafter. This turn-in is available all the way to Exalted. Note: in 4.3 there was an oversight which removed the pre-requisite quest Orders from Lady Vashj. You can still purchase the Armaments on the AH but cannot turn them in.Once you are 70 and have upgraded your gear, you can opt to run Slave Pens, Underbog, and Steamvault on Heroic Mode. They award significant reputation: regular mobs are worth 15 reputation, 2 for non-elites, and 150/250 for bosses. This method works until Exalted.Revered to Exalted
Continue with the same strategy as above: finish any remaining quests and run Steamvault.
It is also possible to run Slave Pens, Underbog, and Steamvault on Heroic Mode. The reputation gained is not much more than running Steamvault in normal mode, whilst the time investment for heroic dungeons is much higher, possibly resulting in a lower net reputation per hour.
Wrath of the Lich King
In Wrath of the Lich King, a new quest hub was added that grants Cenarion Expedition reputation. Completing the quest related to
D.E.H.T.A's Little P.I.T.A. in Borean Tundra will net you a significant amount of reputation. Like other quests, it's best to complete this hub after Honored. Just remember not to kill an animal and then speak to the NPCs, as they will be hostile for several minutes afterwards.