TrueCrypt

T r u e C r y p t
Free open-source disk encryption software for Windows XP/2000/2003 and Linux
Main Features:
Creates a virtual encrypted disk within a file and mounts it as a real disk.

Encrypts an entire hard disk partition or a device, such as USB flash drive.

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, Blowfish (448-bit key), CAST5, Serpent, Triple DES, and Twofish.
Mode of operation: LRW (CBC supported as legacy).

http://www.truecrypt.org/downloads.php

Windows Vista/XP, Mac OS X, and Linux

TrueCrypt 6.2

Changes

- The I/O pipeline now uses read-ahead buffering, which improves read performance especially on solid-state drives, typically by 30-50%. (Windows)

- The boot loader now supports motherboards with BIOSes that reserve large amounts of base memory (typically for onboard RAID controllers). Note: In order to be able to take advantage of this improvement under Windows Vista, you will have to install Servic

- Mounting using the 'Auto-Mount Devices' feature may take significantly less time as partitions containing unencrypted filesystems are now skipped. (Windows)

- When volumes that are mounted as read-only or removable are saved as favorite volumes, they are mounted as read-only and/or removable when 'Mount Favorite Volumes' is used

- When a multiple-pass wipe algorithm is selected when performing in-place encryption of a non-system volume, the header areas will be wiped before the encrypted headers are written to the disk. Note: On an existing volume, you can perform such an operatio

- Many other minor improvements, bug fixes and security enhancements. (Windows, Mac OS X, and Linux)

http://www.truecrypt.org/downloads

TrueCrypt 6.2a

Latest Stable Version - 6.2a

* Improved file container creation speed on systems having issues with write block sizes greater than 64 KB. (Windows)
* The 'Device not ready' error will no longer occur when the process of decryption of a system partition/drive is finished. (Windows)
* Other minor improvements and bug fixes. (Windows, Mac OS X, and Linux)

http://www.truecrypt.org/downloads