BoxCryptor: Cloud storage encryption
BoxCryptor allows you to encrypt entire folders using the AES-256 standard. Any file stored in the virtual BoxCryptor drive is individually encrypted and stored in the destination folder.
The folder containing encrypted files can then be uploaded to the cloud by providers such as Dropbox, Google Drive or Windows Sky Drive.
BoxCryptor is available on Windows, Mac OS X, iOS and Android and can be used by private users for free on all platforms.
An Unlimited version is available for 29.99€ and targets users that need special features (like support for multiple encrypted folders). Business users pay a one-time fee of 69.99€ per user to use all desktop platforms.