AES Crypt AlternativesTop File Encryption Software and other similar apps like AES Crypt

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

GnuPG allows to encrypt and sign your data and communication, features a versatile key management system as well as access modules for all kinds of public key directories. GnuPG, also known as GPG, is a command line tool with features for easy integration with other applications.

Platform-independent password-based authenticated encryption of files & folders.

Kleopatra is a certificate manager and a universal crypto GUI.

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.

AxCrypt is a simple file encryption software for Windows. It integrates seamlessly with your workflow to encrypt, decrypt, store, send and work with files.

BitLocker Drive Encryption is a data protection feature that integrates with the operating system and addresses the threats of data theft or exposure from lost, stolen, or inappropriately decommissioned computers.

Encrypto lets you encrypt files before sending them to friends or coworkers. Just drop a file into Encrypto, set a password, and then send it however you normally would — but this time with added security. It’s free for both Mac and Windows.

A simple, modern, and secure encryption tool.

SiriKali is a Qt/C++ GUI application that manages ecryptfs,cryfs,encfs,gocryptfs and securefs based encrypted folders. These projects are compared here.SiriKali can also connect to ssh servers using sshfs.

A simple, modern and secure encryption tool (and Go library) with small explicit keys, no config options, and UNIX-style composability.

Boxcryptor is an easy-to-use encryption software optimized for the cloud. It allows the secure use of cloud storage services without sacrificing comfort.