This probably is not any good for non mud ponds or ponds that already have water flowing through. If like me you just want something to remove pine needles, dust, pollen etc then this could be for you. Here is a video of it in action, sorry for the quality.
http://www.youtube.com/watch?v=JThWzc0X_Q8
It runs off of airlift and can handle changes in water levels of about 15cm. There is more water flowing through the skimmer than what you see exiting in the video given there is an exit under water also. I simply use a skimmer net to reach in and remove the stuff collected on the top inside the skimmer on the water surface. I have two of them placed in the pond in the areas wind blows the stuff floating on the surface. They do a great job for me given my pond shape and are very cheap to run. No worries about a water pump running dry either etc.
I can post a diagram of how its made if anyone is intrested. This is a mk1 of the system and I think it can be improoved upon.