Not sure where best to put this, because it's not specifically about Mulch, but just a fun way to explore composition which seems to be something many Mulchers are interested in doing.
Anyway, from time to time I take part in this thing called the Disquiet Junto, where a guy sets everyone a weekly challenge and you just have the weekend to try and respond to it. Last week's challenge was to make a piece of music using only the sounds of a turntable - with the limitation that you couldn't play a record. This week's is to use the intro sound from a particular radio show and make music with only that.
There's no compulsion to get involved every week, just whenever you can and want to.
Here's the original explanation of the Disquiet Junto: http://disquiet.com/2012/01/27/the-disquiet-junto/
Here's the Soundcloud group where people discuss and share stuff: http://soundcloud.com/groups/disquiet-junto
The Junto is one of the few contexts were people leave comments on Soundcloud that say more than "YAY! Listen to my stuff too if you have time."