Well, I don't know about an independent cataloguer, but what I do is encode all my CDs to FLAC, so I have lossless quality and the convenience of playing from a server, therefore my library is through my media player (Monkey or Songbird) and is pretty tight. Every disc I encode gets all the art picked up by MuvUnderCover and I use dbPowerAmp to process the FLACs and that uses CDDB amongst others to pull the data down.