Making money with cooking.

There are several great ways to make money with cooking in Lich King.
First and most obvious, max out your cooking. Currently, at least on my server, this is a cheap undertaking as most mats are dirt cheap.
Next, make several fish feast. These sell for a nice bit on my server and all the mats can be farmed in Wintergrasp during down time at the lake near the Alliance Flight Master.
Also, you can make some decent money flying around and gathering up all the recipes that vendors sell. Anything that you can get from an out of the way place will usually sell, as people are usually too lazy to go themselves to buy them. They would rather buy them from the Auction House out of convenience.