Evan Roth's Animated Gif Mashup 2.0 allows users to mash-up animated gifs found on the web into a collage and add sound. It's a bit like YTMND except you can pile on an unlimited amount of gifs.
Roth launched Animated Gif Mashup 2.0 last week at SPEED SHOW vol.1: TELE-INTERNET curated by Aram Bartholl.