TrueCrypt now does pre-boot authentification

TrueCrypt is an open source on the fly (transparent) whole disk encryption software for Windows, Linux and MacOS that now supports pre-boot authentication on Windows. This means you can use this to replace PGPDisk or BitLocker.

It supports AES-256, Serpent and Twofish encryption, hidden volumes with two levels of plausible deniability and hidden volumes.