A new project at NIST, Computer Forensic Reference Data Sets (CFReDS,
http://www.cfreds.nist.gov/), has posted a few hard drive images for
investigators and academics to work with. Among these is an image of
a Mac filesystem that is available in Encase, iLook, and dd formats.
It's like a rosetta stone for anybody trying to evaluate and process
these forensic file formats!
If you're interested in Forensics here are some available images to test with.