Knoppix 5.0.1 boots rather nicely from a USB key. It's getting easier to get it working, as the USB bugs from the previous versions have been fixed. This is a "recipe" for creating a Knoppix bootable USB key. It was originally posted to the forums: http://knoppix.net/forum/viewtopic.php?t=25402
dmesg | grep -i scsi
dmesg | grep -i usb
cat /proc/partitions
fdisk -l
dd if=/dev/zero of=/dev/sdz
mkdiskimage -4 /dev/sdz 0 64 32
mkdiskimage -4 /dev/sdz 0 128 32
mkdiskimage -F -4 /dev/sdz 0 255 63
mkdiskimage -F -4 /dev/sdz 1 255 63
dd if=/dev/zero of=/dev/sdz bs=1 seek=446 count=64
echo -e ',0
,0
,0
,,C,*' | sfdisk /dev/sdz
mkdosfs /dev/sdz4
syslinux -s /dev/sdz4
mount /dev/sdz4 /media/sdz4
cd /media/sdz4
ls
rsync -av /cdrom/boot/isolinux/* .
mv isolinux.cfg syslinux.cfg
rm -f isolinux.bin
rsync -av /cdrom/* .
rm -rf ./boot
sync
cd /
umount /media/sdz4
sync
mount -o remount,rw /cdrom
mount --bind /cdrom /media/sdz4
vi /media/sdz4/syslinux.cfg
noswap noeject noprompt dma home=scan