As a crafter and player, I'd like simple check boxes/options added to certain vendors and the auction hall:

Unusable Items: I'd like a checkbox for vendors and a search option in the auction house for hiding items that are unusable for my character. Selecting it would make those items not appear on the vendor or auciton hall when searching. The game would remember my preference for this box being checked on vendors.

Hide Known Recipes: There are numerous recipes on the crafting vendors and several on the AH at any given time. I'd like a checkbox on vendors to hide known recipes so I only see the ones I can still learn. A comparable option for the auction house would be nice as well. The game would remember my preference for this box being checked on vendors.

Hide Collected Items: I'd like a similar checkbox to hide collected items on a vendor. Could be implemented and handled by the same button as hide known recipes. so I only see the ones I can still learn. A comparable option for the auction house would be nice as well. The game would remember my preference for this box being checked on vendors

Possible Implementation:
Auction House Pull Down Box:
Filter Results by: None, Hide Unusable Items, Hide Known/Collected Items, Hide Unusable & Known/Collected Items.

Vendor Checkboxes:
Box 1: Hide Known/Collected Items
Box 2: Hide Unusable Items.