I have made a slight update to the earlier post at Automatically Ripping FLAC Files to mp3s Via Shell Script. I have updated the script so that it will automatically make the database directory the first time you run it. Without that change, the script wouldn't work as expected unless you manually created the directory.
In addition, I attempted to get the script working on my OS X machine with much success. Installing the Apple Developer Tools (available on your OS X install disc) will provide you with the 'make' command line utility. This will allow you to compile id3 mass tagger. MacPorts and/or Fink will provide you with the other tools you'll need - lame, flac, and metaflac. I was able to compile and install id3 mass tagger without any problems (much to my surprise).
Once you have these tools, the script should work as expected. Let me know if you have any problems and I may be able to help you out.