Well... my first suggestion should be to be able to submit a search query to the auction window, but this might be a little bit less involved to implement.

My suggestion is to move my auctions from the post tab to a new tab (named "Posted" or "My Auctions" or something similar); and in the space where the posted auctions used to be, a list of currently posted items in the auction house that match the name of the item you are posting.

This will give a person the chance to post an item with a competitive price without needing to sift through 6 or more pages looking for a specific item name over and over.