How do I run linux off of an external hard drive

I have an iMac running Mac OS X 10.5 and Windows Vista Premium via Boot Camp, and I wanted to experiment with Linux, however my internal hard drive is pretty much maxed out, so I can't really create a third partition for Linux. I was wondering if there's a way to run Linux off of my 500gb external hard drive without having to take apart my computer. I plan on using Ubuntu as my Linux OS. If it's possible can you please provide a step-by-step guide?

Thanks,
Max

I don't think the install process or setup is necessarily that different from a regular setup. The only thing I would be worried about would be speed and whether or not it's a firewire connection. I have a friend who's done it (jimb930 on here) and he ran Ubuntu off of his external hd without much issues except his bootloader. Basically what happened was he installed the bootloader to the external drive so he couldn't even boot Windows without the drive plugged in. Other than that, its fairly easy I would guess. A quick Google search will no doubt bring some info up.

(To fix the bootloader issue, I would first install LILO or GRUB on the main machine first, then when the distro of choice asks for the installation path of IT'S bootloader, just install it to the root partition of the Linux installation. In this case, it would be the external hd path. So what will happen is that a bootloader will load a bootloader. Yes, it'll still work.)

If you want more detailed instructions, I'll try and help.