Ocyptamus fuscipennis (Hoverfly).
Size: approx. 3-5 mm. Photo: 06/27/11, noon.

I watched this small hoverfly for 10 min plus and it is quite a nervous insect. It looks like it wants to land somewhere but then takes off again. I never got a really good shot. Anyway, this is Ocyptamus fuscipennis. There seems to be no English name for this little fly. The photo below shows a top view of what I believe to be the same individual. 
bug guide: