Debian distros that boot from USB ["Keydrive"] using DebianInstaller or similar way:
- They are under 64Mb.
- They can use the direct Bootability to the USB Key from the Motherboard (["USBKeyBootable"]) or use a Floppy to boot the USB Key (["USBBootFloppy"]).
DamnSmallLinux , see ["DSLinuxUsbKey"]
[http://www.flonix.com/ Flonix], that includes the Keydrive hardware.