Software: iTunify

I haven't yet tried this, but I am tempted. iTunify is the "missing tools for iTunes".

With iTunify you can: find duplicate tracks; find and replace in I3 tags; change the case of ID3 tags; exchange ID3 tags; import and export artwork; import and export ID3 tags; toggle the bookmarkability of AAC tracks; remove “dead tracks” from the library; remove checked tracks from the library; remove unchecked tracks from the library; and invert check marks. You can do all this without leaving iTunes. iTunify also comes with a variety of pre-written templates. The software is a Universal Binary product, so runs natively on both PowerPC and Intel Macs.