Tools - Addons
Auctioneer
The Auctioneer addon is so powerful, it has its own page here at makewowgold.com. Anyone claiming to unlock the 'secret' of gold-making in WoW will, inevitably, be relying on this addon. It has some extended features, though, which are worth mentioning here: BottomScanner and Enchantrix. It's also worth checking back at AuctioneerAddon.com from time to time, since Norganna (the creator) releases good updates. Personally I'm using the alpha version of Auctioneer Advance. Even though it may not be 'released' yet, it still has great features that I like.