OSX is awesome for por...... saving Passwords
Just open Disk Utility and make a new image, set the size to something that you wont ever reach, and choose "AES-128" as encryption, and "selfgrowing image" as format. (Im using a german osx, dont know the exact english description).Only use good passwords, and dont add it to the keychain(!)
Its similar to "truecrypt" in the windows/linux world.