This guide is basically for those who are also tired of all money guides being for epic'd out level 70's running instances. Instead this is for people between 60-70 who aren't super l337 yet, so hopefully this will help.
In OL, your target mobs are the Blistering Rot located in the Pools of Aggonar of the Hellfire Peninsula.
There are many, many of these mobs there, with decent respawn rate. The point is, they drop "Corrosive Ichor," which vendors for 8.7 silver.
8.7 silver though? One may not think that's a lot, but these mobs have considerably low HP, with considerably low attack power.
The main mob is also accompanied by 2 minor mobs, but don't let that put you off; the minor mobs are virtually 1 shot kills. All three mobs, the 2 minors and the main mob, have virtually 100% drop rate for this ichor. So 3 ichor for 1 kill in total.
A stack of ichor vendors for a little over 1.7g- I realize this isn't ground-breaking money, but for the effort needed and the availability, I thought it was pretty decent.
I hope this helped, good luck people.
-Oz