cryptmount is a utility for creating and managing secure filing systems on GNU/Linux systems. After initial setup, it allows any user to mount or unmount filesystems on demand, solely by providing the decryption password, with any system devices needed to access the filing system being configured automatically. A wide variety of encryption schemes (provided by the kernel dm-crypt system and the libgcrypt library) can be used to protect both the filesystem and the access key. The protected filing systems can reside in either ordinary files or disk partitions. The package also supports encrypted swap partitions, and automatic configuration on system boot-up.
FreeOTFE4PDA is an "on-the-fly" (OTFE) transparent disk encryption program. Using this software, you can create one or more "virtual memory cards" on your PDA. Anything written to one of these cards will be automatically and securely encrypted before being stored. A PC version is also available, allowing data encrypted on your PC to be read/written on your PDA, and vice-versa.