Encfs

on osx

You will need brew installed.

$ brew install encfs 

This will take some time, as it downloads all of your dependencies. Now to create your first encrypted directory. The encrypted data will be stored in .crypt, and when you mount it, it will be ~/crypt in your home directory. You could replace ~/.crypt with ~/Dropbox/Private to store your encrypted drive on Dropbox.

$ encfs ~/.crypt ~/crypt

To umount it, make sure you're not in the directory (~/crypt in the above example) and:

$ umount ~/crypt

You can mount it elsewhere later if you wish:

$ encfs ~/.crypt ~/newcryptdir