recent
filesystem types, but I wouldn't want to try to dig through a
 Solaris disk on a VMS machine.  Once I knew what the filesystem of my 
    I don't believe someone (beyond Tony) would do that ;o)
  house, odds are a hard disk or floppy image is
going to be AmigaDOS
 (FFS or OFS), MacOS (HFS), DOS/Windows (FAT or NTFS), RT-11, OS/8,
 CP/M, TRSDOS, VMS (ODS-1), SunOS 4, Solaris, Linux (ext2 or ext3), or
 perhaps some flavor of BSD - I'm sure others here have greater a
 lesser chances for those and more). 
    Maybe an open-source program which could open an image file and
 "autodetect" it, saying which format/os/etc it is? :) 
 
I've thought about that in the past for floppy formats - but there are just
too many, and too many that are close in implementation, and too many others
that always need a little assistance in the decoding.
In terms of hard disks, I hate to think how many SysV-type variants there are
around :-)