OK. I said I wasn't going to do it, but it was driving me nuts. I wrote another addon called Last Listed for the Auction House.
The short version is that it helps you sells stuff by remembering the last price you listed an item and performing an auto-search to view what other people's auctions for similar or exactly the same items. You don't do anything special, just drop the item in the normal Create Auction spot.
Per the latest patch notes, Mythic appears to have possibly made my next addon idea unnecessary. Basically, I was going to write an addon that auto-greeded anything that wasn't usable by you.