Auctioneer

Auctioneer is an addon that allows you to view information about an item that may be useful in helping you determine what it’s worth. Straight out of the box, Auctioneer knows much about many items in the game, and will tell you many things about the item when you move your mouse over the item in the game.
This plugin also provides you with in-game data on data that is collated by you at the auction house. You trigger the data gathering by either clicking the “Scan” button on the main page of the Auction House, or by typing “/auctioneer scan” manually.