We had a hard crash of our Mac Mini the other day. It wouldn't boot after a hard power reset. Don't ask -- I'm trying to protect the innocent ;-)
My wife used to work at Apple, but I'm not a Mac man, so we brought it in to the "Genius" counter at a local Apple store. The guy was pretty helpful but he said there was no hope to recover the disk. However, I've been using computers long enough to know that this was some kind of file system error that was largely recoverable, and we had some data that wasn't yet backed up.
Using a Windows box, I could pull some data off a separate Mac HFS partitioned FireWire disk with the useful HFSExplorer. But to get to the internal drive I had to boot the Mac Mini from the boot disks. Various attempts at the GUI Disk Utility (from the installer) and fsck_hfs didn't help much. The file system was pretty corrupted.
Web pages suggested using Disk Warrior or Data Rescue II. I suspect they would have helped either fix or recover files, but I didn't want to shell out $100 for either.
On a Windows machine, I would have just booted to Knoppix and tried fixing with Knoppix. But I didn't know if Knoppix would work with a Mac Mini.
Our Mini is an Intel Dual Core model, built late 2006 (I think). A Knoppix Hacks book indicated you could boot newer Macs from CD, so I gave it a try. After burning the Knoppix 6.0.1 iso to CD the Mini booted straight away.
Knoppix' built-in PhotoRec recovery tool is now recovering our files. The tool has a command line interface, but it works for me. It's slow (taking 24 hours plus to recover all files), but I'm pretty sure it's quite comparable to what I'd see in commercial tools at least as far as performance.
Anyway, Knoppix 6.0 has a cool window manager called LXDE, so I may look to use LXDE in an upcoming distribution called Lubuntu.