Getting something to boot from a usb key

Well, I've now got some experience with these usb keys and it seems they do have quite a few limitations.
First, they don't seem to tolerate any more partitions than two
Second, FAT32 and FAT16 seem to be the favoured file systems and you can have twoo partitions with these fs's. However, I wasn't able to get any more than one partition with either EXT3 or reiserfs.
Then, it just doesn't seem to be quite as straightforward to copy stuff to and from a usb key as it is to a usb HDD.
Another problem, is that my MacBook seems even more reluctant than the Dell desktop to even "see" the usb key.
Nevertheless I did manage to get a Linux OS onto my key. This is Puppy Linux which i got from this guide.
This was actually very straightforward apart from two minor problems.
First, my Mac just didn't see the usb key so I couldn't do the installation there. When I moved over to the Dell, everything worked fine.
Secondly, the guide is meant for computers that will allow booting from a usb drive which, unfortunately, neither of my computers do.
So, I had to add the following to my /boot/grub/menu.lst on the Ubuntu partition on the Dell:

title PuppyLinux 3.01 (on /dev/sdc1)
root (hd0,5)
kernel /boot/puppy/vmlinuz root=/dev/sdc1
initrd /boot/puppy/initrd.gz
savedefault
boot

as well as putting the two files, vmlinuz and initrd.gz inti /boot/puppy/ on the Ubuntu partition.
Then it booted without problem.
I'll talk a bit about Puppy Linux itself tomorrow.

Boot to a usb flash drive

Because i couldn't stay too interested in Sabayon, I thought I'd like to install some Linux OS (I was thinking either Zenwalk or Puppy Linux) to a usb flash drive and boot to it.
My original thought was to do this through Grub on the Ubuntu partition (as I have on the MacBook and the Dell desktop).
However, I've come across this HowTo which actually allows you to boot directly from the thumbdrive (unfortunately, neither of my machines allow booting from usb devices).
I've been trying to partition the usb drive using Parted Magic but it's turning out to be surprisingly difficult.
Originally the drive had one partition (FAT32, 3.9GB). I tried to break this into to EXT3 partitions. While the first stayed as EXT3, the second became "Unknown". I've tried this over and over, but cannot get any more than one large partition, even with FAT32.
Something very strange here and the Wikipedia article mentions nothing about this.
I should mention that my usb drive DOES have a READ-WRITE switch (a real, physical SWITCH) on the side. You must turn this to RW (pushed towards the bottom of the drive) for any formatting work.