Mag'har and Kurenai
The Mag'har and Kurenai factions are one of the easiest factions to raise in the Burning Crusade. The Mag'har faction is for Horde and the Kurenai faction is for Alliance. Both of these factions have their main hubs in Nagrand. As stated earlier these factions are very, very easy to raise. The ogres in Nagrand will give you 10 reputation per kill. The ogres here have roughly a 25% chance per kill to drop Obsidian Warbeads which can be turned in for 100 reputation for 10.
However if you plan to raise you consortium reputation I recommend you save these prayer beads for that. The Mag'har and Kurenai reputations are two more reputations that will greatly help you achieve the 75 mounts achievement. For the location of the best ogres to farm look on my map below.
The Mag'har and Kurenai are involved in two achievements. One to reach Exalted with them and the other to buy the mounts they sell. (Which just go towards the 75 mounts achievement). I also have a video of me farming the Ogres for the Maghar and Kurenai reputations. If you'd like to see the video click on the link below.