Auto Coverfinder and Good Dupilcate Cleaner

update: the music brains link below works pretty well, it doesn't do cover art, but that feature was added today!

My iTunes collection is a mess, being as the music originally came from rips of my CDs made a few years ago from a Linux box, most of those still exist, but for the most part they don't have any cover art. Additionally because of back concern and sordid attempts to organize it all properly, the music remains a mess and there are several duplicate tracks.
Does anyone have links to tools that will help with this? I know that iTunes has a dupe feature, but it is a bit lacking as it only matches on song name and so if the same song is there twice but from two different albums it doesn't help much. (Ideally if you have only one copy of the song and a pointer that would be great but I think beyond what iTunes can do)
Also is there a way to create a smart playlist that will only show songs without cover art? I don't see how to get access to that from the playlist creator.