SitePoint: Portable Linux Virtual Machines

“Quite the buzz is building over the technology preview released
by MetroPipe. This package runs on Damnsmall Linux and uses QEMU (a
CPU emulator).

“Essentially an Internet communication system, it can run
entirely on a USB mini-drive key (128 MB) and other flash-media
devices, and even iPods. It includes a bootable Linux OS, a web
browser (Firefox), email client (Thunderbird), Enigmail GPG (for
email encryption) and a persistent home directory…”