It IS possible booting Linux from a USB on useless, stupid MacBook Pros (I own a brand new one and I HATE it). You just need to first boot unto a CD that allows you to boot from the USB (stupic Mac):

Hmmm....so Apple should automatically create their systems to work with every possible build and feature of Linux right out of the box? IMO they don't support such a configuration because it would be too much of a troubleshooting problem. Their phone support is rated at least 20% higher than any pc company, and trying to support more operating systems than just their own could create a pretty severe decrease in the quality of their phone support. I don't think Apple needs to spread themselves thinner to support edge-use cases. Their strength lies in the fact that they have more control over things than the average pc company. I'd rather have a stable OS X than full support for 10 different operating systems on the hardware. Why not buy different hardware if you don't want to use their operating system? I understand wanting to dual or triple boot a mac, but I really don't expect it to be seamlessly supported by Apple.

- Peder

So close, yet so far: we have an installation onto the iPod, but can't boot from it. Does anyone know exactly why this doesn't work?

It's because you're on a Mac. Macs actually don't have support for booting 'legacy operating systems' (read: anything that's not OS X) from external hard drives. In other words, your Mac boots Windows simply because it's a "bail-out" alternative. If you didn't have Windows installed it gives an "invalid boot disk" error message if I recall correctly.

Has anyone tried to use rEFIt as the boot manager, to point to the ipod???

That won't work either. rEFIt is nothing more than a bootloader, which means that it still cannot detect/boot non-OS X volumes on external hard drives. If you try it, it'll give some error message saying that Apple's firmware doesn't support it.

Thanks anyway :)