How do I put Ubuntu on a USB drive?

[aescnt]

?

[lisati]

If you have already installed the latest version, there is an option on System->Administration that does this for you. Have a look here: https://help.ubuntu.com/community/Installation/FromUSBStick

[Kareeser]

As far as I know, lisati's suggestion creates an Ubuntu bootable "Live-USB" type of structure, so you can install Ubuntu on other computers using your USB key instead of a CD.

If you were inquiring about installing Ubuntu straight onto a USB key, you can go ahead by using a LiveCD to install it onto the USB key... I don't know how to put it more simply :)