During a segment of The Hour (one in which I was very lucky to be a part of) they showed a backwards clip of a man singing Stairway to Heaven in reverse. Here is some guy doing the same thing, but with a more patriotic song. All the activities he preforms are to add a little spice to the reverse section of the piece.
[What Song is this? – YouTube]
I don’t know if this would count as truly backmasking, but it’s close enough that some of you may find it interesting.