ANIMATED GIF MASHUP by Evan Roth (via F.A.T.)
This has been around for a while - a web based tool / toy that creates pages (or, I suppose, collages) with gif animations with added music. All the files you use have to have a URL, and animations are arranged by co-ordinates, but there should be many excuses to be creative / abusive with it.
The above image is taken from one of the examples, called Gif Mashup Dance Sequence #001 (music NSFW). The tool has also been used to create gif based music videos such as this and this.