Besides mechanically clearing the pond by raking out crud as suggested above, maintain clear water by adding plants that will absorb nutrients before algae gets to it. Hybrid lilies (not the wild ones, they take over!), arrow plants, bull rush, etc are all great candidates. Cattails and that switch grass are too aggressive to allow getting a toe-hold.
There is a lot of info here on maintaining a pond. Welcome aboard!
http://forums.pondboss.com/ubbthreads.php?ubb=showgallery&Number=446940A post earlier this spring about my clear water. It isn't looking so pristine now as the strong sun is causing O2 bubbles to lift algae and leaves from the bottom and float some nasty blobs around. It should clear up in a few days though as that algae type appears to be a cold water lover, and the leaves are decaying quickly.
