An unhappy event happened to a cheese-maker friend -- he hadn't made any back-ups of his old G3 tower, and naturally the hard disk went down along with all the recipes of his award-winning cheeses. I tried all the usual -- TechTool, DiskWarrior, Disk Utility -- but they all just threw up their (figurative) hands in horror and simply gave up. (Disk Utility would see the disk, but not mount it).
In a fit of desparation, I told Disk Utility to make an image of the seen but un-mountable partitions. And quite surprisingly, it worked!
I have yet to verify that his important data is there (he lives a couple of hundred kilometres away, and won't be back here for a couple of weeks), but it all *seems* to be there. It reminded me of the good-old-Apple ][ days when a dead floppy could often be resurrected by simply copying it.
I hope that someone else may benefit from this simple fix.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20051123181231470