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.
AES Crypt is an advanced file encryption utility that integrates with the Windows shell or runs from the Linux command prompt to provide a simple, yet powerful, tool for encrypting files using the Advanced Encryption Standard (AES).
AxCrypt is a simple file encryption software for Windows. It integrates seamlessly with your workflow to encrypt, decrypt, store, send and work with files.
EncFS provides an encrypted filesystem in user-space. It runs without any special permissions and uses the FUSE library and Linux kernel module to provide the filesystem interface. You can find links to source and binary releases below.
The author has agreed that EncFS in its current form is dangerous (to security) for several reasons. Wikipedia has a brief summary: https://en.wikipedia.org/wiki/EncFS#General_Security_ConcernsThe actual audit, which the author participated in, is here: https://defuse.ca/audits/encfs.htm
Platform-independent password-based authenticated encryption of files & folders.