Fly to Icecrown and go to this spot here:
When those mobs are killed fly directly down as the picture shows. There will be another group of mobs.
When you alternate between the packs of mobs you will get ~100charms in 10minutes, when you kill one pack and fly up/down to kill the other the other mob pack will respawn in about 5 seconds making it very ideal to farm charms and even frostweave cloth or WotLK greens!
This spot is almost always empty on my server. On the first day this event went live I farmed here until I got the mount and sold it for 70k.
Good luck farming!