If you have a large collection of music in iTunes, it's pretty easy to miss an album or two from an artist you love. Discographer scans your iTunes music library, then shows you all the albums from that artist that you're missing.
All you need to do is upload your iTunes library XML file (located at
/Users/username/Music/iTunes/iTunes Library.xml) and wait a few minutes while Discographer scans the file. When it's done, you'll get a list of all your artists so you can see which albums you're missing. For completionists, it's a pretty handy way to round out your collection. Plus, your library info is never uploaded, shared or saved.