Hiding data in images - Steganography
Either a good way to conceal data, or an under-utilised way of compressing information when sending it alongside images - either way, Steganography is a neat idea. Sadly, generally used for nefarious purposes.
Alex Kelleher’s blog explains more.

Dora Zimmerman:
I am surprised how data can be hidden in images.
November 13, 2008, 9:58 am