Mach-O FS (no really, MacFUSE does rule)
It needs some polishing and more functionality before I’d call it useful, then I have to find out whether I’m allowed to do anything with the source code ;-). But this is at least quite a cool hack; exploring a Mach-O file (thin or fat – in this case, I used the OmniDazzle executable which is a fat file) as if it’s a file system. FUSE of course makes it easy, so thanks to Amit Singh for the port!