Around here they usually recommend bass, bluegill and channel catfish. They stock the bluegill at a rate of 5 bluegill per one bass. The channel catfish ar egood eating and grow quickly, but don't tend to reproduce well, unless given nesting boxes to hide their young in.
Depending on the water temperature and oxygen content, trout are a good fish. You can plant them in the fall when the water cools down and fatten them up over the winter. They are so agressive that you can catch most of them out in the spring before the water temp rises and the oxygen depletes.
One thing to avoid in a small pond is open water fish like perch or crappie. They don't do well and tend to overpopulate.
They say that a given body of water can support a fixed number of pounds of fish, related to the nutrients in its watershed. That is, if a one acre pond can support 1000 pounds of fish, those fish can be 100 ten pound fish, 1000 one pound fish, or 10,000 one tenth of a pound fish(which is what alot of people end up getting after a few years). So it is important to maintain the proper ratio of bass to bluegill to keep the predators numbers high so the bluegill don't overpopulate.
Check with your local extension agent on fish ponds in Penn.
<A target="_blank" HREF=http://pubs.cas.psu.edu/FreePubs/uh137.html>Click here for
http://pubs.cas.psu.edu/FreePubs/uh137.html </A> It is a site for fish pond management in Pennsylvania. There is a link at the bottom for a rather large PDF file.