Tails is a live DVD or live USB that aims at preserving your privacy and anonymity.
It helps you to:
use the Internet anonymously almost anywhere you go and on any computer:
all connections to the Internet are forced to go through the Tor network;
leave no trace on the computer you’re using unless you ask it explicitly;
use state-of-the-art cryptographic tools to encrypt your files, email and instant messaging.
See on tails.boum.org