Auctioneer

The mother of all gold related addons. This baby will change your way of doing business. Auctioneer will automatically pimp your Auction House UI with all sorts of tools to boost your buying and selling methods. When you search for an item it will store data that will show on your tooltip so you can know what is worth what -roughly- without even visiting the AH. download link

Before you start using this tool to buy low sell high; I recommend you use the Scan option and continue doing it for atleast two weeks. It would be even better to do it twice a day thi will give you more accurate data. The scan will take around 15-20 minutes to complete, during the scan you can't do anything so stretch your legs, grab a cup of tea or take a smoke break.

I am not going to go in depth with this addon, because the project is making gold while killing stuff, so instead I'll give you these links that I think will be helpfull.

Part 1
Part 2