After several years of development and regular releases, Tails a live Operating System that can be start from CDRom of USB key, aiming at preserving the privacy and anonymity of your usage is now in its 1.0 milestone.
Several whistleblowers (Such as Edward Snowden), activists, and people seeking for anonymity are using Tails as their daily OS.
Based on Debian, Tails comes with several built-in applications pre-configured with security in mind: web browser, instant messaging client, email client, office suite, image and sound editor, etc. For example,all software is configured to connect to the Internet through Tor (If an application tries to connect to the Internet directly, the connection is automatically blocked for security)
You can use Tor, or Freenet or i2p for your connections, but Tails also includes encryption softwares and security addon/configurations such as HTTPS Everywhere plugin for Firefox, Claws Mail client with GnuPG support, LUKS for USB stick encryption, TrueCrypt, and many more.
If used as LiveUSB or LiveSD, you can also enable the persistence to keep all your changes, files, by creating persistence volume on the free space left on your device. Although the volume will be encrypted to avoid unauthorized access, the use of a persistent volume in a system which is designed to provide anonymity and leave no trace is a complicated issue.
If you seek anonymity and respect of your privacy, Tails is most probably the best Operating System. If for example you are travelling in doubtful country or will leave in a seedy hotel, etc… you better bring a SD card or USB with Tails on it….
You can download the latest version here through torrent or regular HTTP connection. (If you use torrent, please keep in seed to help spread the ISO). You could use for example Unetbootin to copy the ISO on the USB key.
The next release, v1.1 will be based on Debian 7 and be released in June.
For more information, I suggest you to visit the official website.