I thought it might be fun and advantageous to share some of our profit makers.
One of my biggest items that sells for a great profit is gromsblood. It's pretty rare on my server, and people are almost always posting it for 2g per item or less. I buy them up and sell them for just under 10g per item and they almost always sell on one cycle of a 24 hour posting.
Another great one is the 1g+ vendored cooking recipes in Booty Bay. I can't remember their exact price, but they're in the range of 1 to 2g, and they sell on the AH for almost 50g a piece. They don't sell on every cycle, but **** close to it.
Something I've been doing a few times a week is using my mage to port to each major city and doing a limited supply/pet vendor run. That's been a great profit maker. Between that, buying and selling herbs, and searching for resale items I've been pulling in about 2k gold a week for the last month or so. Not wonderful by any means, but definitely nothing to scoff at.
My bank toon just by herself has almost 3k on her, which puts me at a nice place to start really raking in the dough with resale items. Just yesterday I found a formula for the Crusader enchant on the AH for about 200g. Auctioneer said I could make a profit of some 300g or so, so I looked at the price on wowhead and made sure there weren't any others on the AH before I bought it. I put it back up for just under 600g and it sold this morning before I went to class. :D