TrueCrypt is an open source software to encrypt volumes of data. It even supports the creation of virtual encrypted volumes which is portable.

CipherShed is a planned source-available disk encryption program for on-the-fly encryption.

VeraCrypt is an open-source utility used for on-the-fly encryption (OTFE). It can create a virtual encrypted disk within a file or encrypt a partition.

LUKS is the standard for Linux hard disk encryption. By providing a standard on-disk-format, it does not only facilitate compatibility among distributions, bu…