Bukkit

A wishlist for each user and a public summary of it (top 10 most sought after items) would be awesome!

Buyers could put up items they need and suppliers can see what the customers want!

Maybe a notification when an item on your wishlist is put up for sale?

That or I could add an auto buy thing, something like: I will buy X gold ingots that are sold for less than Y. And it will start at the cheapest and buy them all, if none are found for that price, it will wait until there are some.

Because I am already working on this. :P

@Exote: Go

Nooh! I demand that you seize working on that and start working on my really similar (but obviously much better) idea right this instant! D:

I would enjoy something like this, or what Exote mentioned in the comments.

@Exote: Go

This would work great. Are you planning a system to see what materials are in demand? This is a frequent request on my server.