EncFSMP!

[TrueCrypt is not exactly "Open Source", but the source is available. See the reviews to get more information.]

LUKS is the standard for Linux hard disk encryption. By providing a standard on-disk-format, it does not only facilitate compatibility among distributions, but also provides secure management of multiple user passwords. In contrast to existing solution, LUKS stores all setup necessary setup information in the partition header, enabling the user to transport or migrate his data seamlessly.

Boxcryptor is an easy-to-use encryption software optimized for the cloud. It allows the secure use of cloud storage services without sacrificing comfort. Boxcryptor supports all major cloud storage providers (such as Dropbox, Google Drive, Microsoft OneDrive, SugarSync) and supports all the clouds that use the WebDAV standard (such as Cubby, Strato HiDrive, and ownCloud). With Boxcryptor your files go protected to your cloud provider and you can enjoy peace of mind knowing that your information cannot fall into the wrong hands. »

No encryption of dynamic disks, but command-line-encryption! Dynamic disks must be converted to basic disks with EasyUS Partition Master or Partition Guru before encrypting with Bitlocker. Windows BitLocker & "Bitlocker To Go" Drive Encryption is a data protection feature in Windows 10 Professional, Windows Vista Enterprise and Windows Vista Ultimate for client computers and in Windows Server 2008. BitLocker protects against data theft or exposure on computers that are lost or stolen, and offers more secure data deletion when computers are decommissioned. Bitlocker To Go (BTG) is essentially Bitlocker for external drives. It’s full volume encryption for all your USB drives: http://blogs.msdn.com/b/rockyh/archive/2009/03/01/bitlocker-to-go.aspx »

Cryptonite brings EncFS and TrueCrypt to Android. You can browse, export and open EncFS-encrypted directories and files on your Dropbox and on your phone. On rooted phones that support FUSE (e.g. CyanogenMod) you can also mount EncFS and TrueCrypt volumes. TrueCrypt is only available as a command-line version at this time.

The Gnome Encfs Manager is an easy to use manager and mounter for encfs stashes. It allows you to create encrypted directories, any file that is placed in such a directory will be encrypted.

DiskCryptor is the only truly free solution, provided under GNU General Public License (GPLv3), which offers encryption of all disk partitions, including the system partition. The main criteria for open-source software is the availability of its source code under one of the open source licenses. The only open-source alternative to DiskCryptor that has comparable features is TrueCrypt. However, because of the restrictive license under which TrueCrypt is provided — the TrueCrypt Collective License — TrueCrypt cannot be classified as a truly free software, as it places limits on the use and modification of its source code by developers. There are other alternatives with similar functionality, but they are fully proprietary ones, which makes them unacceptable to use for protection of confidential data. »

FreeOTFE is a free, open source, "on-the-fly" (OTFE) disk encryption program for PCs running MS Windows and Windows Mobile PDAs (FreeOTFE4PDA).

This is an experimental project of porting encfs to the Windows world.

Securely encrypt your private and confidential files or whole folders.The encryption/decryption process is simply done by dragging the selected file(s) or folders(s) to application window.Files are encrypted using strong encryption algorithm: AES (Rijndael) 256bit, RC6 256bit, Serpent 256bit, Blowfish 448bit, Twofish 256bit, GOST 256bit + (Threefish 1024bit and SHACAL-2 512bit for Pro Version) ciphers are available.Cross-Platform (Windows, Linux, Mac OS X, ...) GUI Version and Command Line Version are available.Compatible with the Secret Space Encryptor for Android.A wide range of compatible platforms (desktop and mobile) allow easy sharing of protected data.Easy to use. »

LUKS Manager provides on-the-fly encryption (AES by default) to virtual folders on Android devices.

Sookasa transparently protects files across the Dropbox cloud and linked mobile devices, while preserving the native Dropbox user experience on Windows, Mac, iOS and Android.

CryFS encrypts your files, so you can safely store them anywhere. It works well together with cloud services like Dropbox, iCloud, OneDrive and others. The goal of CryFS is not only to keep file contents, but also file sizes, metadata and directory structure confidential.

CyberSafe Top Secret is an information security program that uses modern encryption algorithms (RSA, AES, BlowFish, etc.). The assortment of tools and features provided by CyberSafe Top Secret are valuable in all fields that work with information: protecting confidential information, protecting E-mail correspondence, creating and validating digital signatures.CyberSafe Top Secret supports encryption on the basis of Public Key Infrastructure, and allows you to encrypt computer hard drives partitions, create encrypted virtual drives of any size, and also hide logical disks and encrypted files and folders on the user’s computer. »