Encryption vs. lack of hosting
Data URI Scheme. (Pardon the lack of in-post explanation, but... this post is actually very large without it.)
Command-line tool for Base64 - encoding, decoding, and what.
There was an mp3 example, but it was too big to stick directly in one post. However, you could always do the oldsk00l alt.binary.whatever method of breaking the base64 up into parts and then posting each in order, to be reassembled into a text file and decoded at the other person's end.