My decoder ring will finally be useful
When hiding an object, in plain sight may be the best approach. Steganography accomplishes this task while hiding the "payload". The common form of this encryption is using images as the medium. Alaa Jebran has created a few examples in Visual Basic to do this. Wikipedia lists multiple additional examples, both downloadable and online, on hiding text and files.
The image on the left actually contains the image on the right.
Images Via Wikipedia