I made a simple compost screening device last summer, I get old leaves from recycling center near by with the truck then I bring them home. I shovel them in and it does a great job of sending bigger chunks down stream but drops smaller stuff through the first screens into a pool or container making it easy to shovel them into garden or into more containers for flower boxes and stuff like that.

This was made from an old door frame/12 volt DC electric fishing motor/some aluminum metal screen and parts from here and there. It is a vibrating type of sifter. I will make a better one soon using small 3.5 or 5 HP gas engine without the head on it using motion of piston as a vibration to cause device to some how shake or buzz screens much like this one does.

I like the way it works, surprising how fast it can filter stuff that goes into it.
[attachment=2:1fhoiicp]sifter ramp.jpg[/attachment:1fhoiicp]
[attachment=1:1fhoiicp]sifter bottom view.jpg[/attachment:1fhoiicp]
See pic below has motor on top and fly wheel, this design was inspired
by "cat in the hat" I think..lol

[attachment=0:1fhoiicp]Picture 008.jpg[/attachment:1fhoiicp]

Below is video of running device on youtube
[video:1fhoiicp]http://www.youtube.com/watch?v=cUi6whhLKQs[/video:1fhoiicp]