A day late and a dolla short for Cold's Gold Factory carnival (which is today, go check it out!).
I was hesitant on posting this information as it has been months since I have done any cross faction trading, but I figured I would help a brother out with a few things I used to do (since Cata, I barely have time to take on my own AH let alone dealing with two!). So here goes:
Although this is a bit of a generic tip, even hitting up the "neutral" AH locations (winterspring, BB, tanaris) to pick up recipies is a very viable flip (most can be picked up for silvers and sold for golds- see a post I did on Tanaris Vendor Recipies). But here is something that I still farm when I have some extra playtime:
The Cat Carrier: Black Tabby "used" to be a great option as well, until it is now considered a zone drop (I farm an elite named Yetimus the Yeti Lord) in the fabled Hillsbrad countryside.
Wanna know my route? EZ peezie. Yetimus is a quest elite that roams a very small area around the caves. You can see from the mini-map screenie above he spawns right around 42, 56 right outside the cave. Due to being a quest elite, he is on around a 60 second timer. Now wowhead.com lists his droprate at around 1 per 1000 for a zone drop for the tabby, due to being an elite it seems it is quite lower. In just shy of 45 minutes farming him/her/it, I received a drop (so I am figuring about 40-60 kills) along with a few greens and a bit of other "junk".
With a selling price of around 4K on Horde side, and around 5.5K on Alliance, it is worth your time if you are feeling "lucky". Well, I gotta ask, "Do you feel lucky punk? Well, do ya?"
Good luck on the farm, and if you are a miner (Silver Vein), herbalist (Straglekelp), or even a skinner (Medium Leather), you can double duty here!