FreeOTFE

FreeOTFE is a free, open source, computer program used to automatically encrypt and decrypt information stored on a hard disk.
FreeOTFE was originally written for Microsoft Windows and was later copied to Windows Mobile (FreeOTFE4PDA).
It can encrypt information using a large number algorithms including AES (aka Rijndael), Blowfish, CAST6, MARS, RC6, Serpent and Twofish.
Sarah Dean is the developer of FreeOTFE.