HOW TO: Creating a Password Protected Folder
A question that doesn’t come up too often but is still a great one to ask none-the-less - encrypted 
folders, how do create you ‘em?
While most people are happy with having their accounts password protected, or even going a step further by having FileVault in place, there’s always one or two that only want certain individual folders encrypted. Other than downloading some third-party software to create an encrypted zip-archive, OS X has a rather primitive yet completely effective method for creating password protected folders, or shall I say, disk images? Apple Matters | AAM: Creating a Password Protected Folder