I would like invite you to know SliTaz.
SliTaz is a free operating system, working completely in RAM and booting from removable media such as a cdrom or USB key. SliTaz is distributed as a LiveCD, and weighs less than 30MB. The system is quick and responsive, clean and robust. SliTaz is simple and intuitive, providing a lightweight, elegant desktop, detailed documentation and easy to use configuration tools.
To see more: http://www.slitaz.org
I am use, and I like!
i think it is better suited in the request forum. Also Puppy linux also installs onto a flash drive and is thus considered "portable" unless you are unable to boot to USB for various reasons. Also in some public libraries and other places with publicly accessable computers it is a violation of their terms and agreement for use policy to run any other operating system than what is installed on the computer itself.