GWAuctions.org is the best Guild Wars auction site. The system is specially designed for trading Guild Wars items, but also implements standard and advanced auction functions.
The most notable part is the Quicklist. Basicly, it's a still growing list of known items that you might want to sell, so you don't have to enter all details about an item.
The wishlist is also a usefull feature, as it allows you to be notified of new auctions that match your filter. This can be anything from simple filters to check the item name, to very advanced filters that search for specific weapon modifications.
This is also the only site where you can actualy "see" the item before you buy it. The seller gives all relevant data, and other people will see the item as if it was in their inventory. That means there is no need for cryptic signs like "20/20 15^50 +30"
You can search for anything about an item. It's name, it's colour and even effects and descriptions. For example, you can search for "+5 Energy" or you can search for "health" to sum up all items that modify your health.
You can view all your own auctions on a simple page and you can track auctions to watch their progress just as simply. You can even get notifications when items are added that you want.
