TrueCrypt is free open-source disk encryption software for Windows and Linux. It offers on the fly encryption of your sensitive and private data.

I personally used PGPdisk to encrypt my important files. There’s only one problem. It has a limitation of 4Gb per virtual drive. TrueCrypt is able to encrypt the whole partition! Best of all it’s free.

TrueCrypt provides 2 great features for enhanced security. In an event where you are forced to provide the password, it has hidden volumes and unidentifiable volumes. Try it out.