DCU

Drag'n'Crypt ULTRA (DCU) is a small and easy to use file encryption program. You drag files to encrypt onto the DCU "drop zone" (or on an icon present on you desktop) and DCU will encrypt files with the very safe Twofish encryption algorithm. Decrypting succeeds just as quickly and easily in the reverse way.
Trick : enable KeyFilesAssoc (LiberKey Tools -> Enable files associations). So, a right click on a file or directory allows you encryption and conversely.