I stumbled on a pretty cool site. It has a couple of audio clips from different artists that when played backwards reveals a hidden message. Coincidence? You decide.

Some of them had me seriously wondering... it'd be too difficult to to plan for this type of effect?

http://www3.telus.net/jefmil/stairwaybackwards.htm

The first one, stairway to heaven takes a couple of seconds to load. The rest of them are pretty quick.