Truecrypt is free and open source disk encryption software for Linux. The below video demonstrates the new graphical user interface for Truecrypt 5, released February 12.

Truecrypt features:

* Creates a virtual encrypted disk within a file and mounts it as a real disk.
* Encrypts an entire partition or storage device such as USB flash drive or hard drive.
* Encrypts a partition or drive where Windows is installed (pre-boot authentication).
* Encryption is automatic, real-time (on-the-fly) and transparent.
* Provides two levels of plausible deniability, in case an adversary forces you to reveal the password:
1) Hidden volume (steganography – more information may be found here).
2) No TrueCrypt volume can be identified (volumes cannot be distinguished from random data).
* Encryption algorithms: AES-256, Serpent, and Twofish. Mode of operation: XTS.

www.truecrypt.com