With the new 3.2 patch you are now allowed to make an opposite faction character on a pvp server. This has opened the possibility to take advantage of the opposite faction's economy variation.
For Example: I got myself a [Razormaw Hatchling]. On the Alliance AH it sells for 2500.
I Make a new Orc character and run him to Orgrimmar AH. Those hatchlings are selling for 3500 on the horde side. I advertise that I am selling cheaper than the AH and once I find a buyer I put my listing on the neutral and the buyer purchases the item immediately.
You can do this with any other item that sells for more on the other faction.
Also, you can do the reverse: If you find that certain things are MUCH cheaper on the opposite AH you can try to convince them to put it on the neutral and add a gift for their trouble.
For example: I found that on Horde AH they were selling Greater Cosmics for 12g/each vs 17g/each on Alliance side. I told the guy if he would put them up on the neutral I'd immediately buy them at 13g and he gladly agreed.
I didn't find anything similar to this when I searched the forums.
Hope you find it useful.
[EDIT] Just an fyi: The Neutral AH's take a 15% cut vs 5% on the normal AH. Keep that in mind.