It isn't often that I'll promote something that costs our readers money. In this instance however, I'm willing to make an exception. Simply put, Gold Wars 2 is the most robust search and refinement tool for Guild Wars 2's Trading Post. Unlike gw2spidy, Gold Wars 2 is all about flipping items quickly, by identifying those you can turn a huge profit on. Gold Wars 2 also allows you to manually calculate large projected sales numbers and store searches and favorites.
I must admit, having only begun to use it it has already made me around 50g in a couple of days, which is a lot considering I've spent very little time at the Trading Post (I'm too busy finishing my legendary). At a cost of $15 for 3 months, it's such a small amount of money for so much (potential) return and considering the number of updates its already had, it's well worth it.
If you don't want to take the plunge however, I have free access for two lucky individuals. Simply drop me an email at firstname.lastname@example.org and the first two who do, will receive their passes. Don't miss out!
[Edit] Crikey, you lot are quick. All free access keys have gone! I will be pairing up with Gold Wars 2 soon however, to give away some more.