How can I open FLAC files in iTunes without doing any kind of conversion?
I've tried Fluke, which has been no
  help, especially since the SetOGG
  script no longer works on Mac OSX
  10.6.


@Phillip Whelan Fluke has had 10.6 support since 2009. If you're experiencing issues with Fluke, which is considered the top offering at present, then I'd be curious about further inspection of the files or your system. Perhaps they are not 16bit/44.1KHz, or wrapped in the OGG Container?