I believe this is a young Black & Yellow Argiope (Argiope aurantia) for a number of reason: the way in which its legs are resting in the familiar X form (which lends to the spider's nickname of St. Andrew's Cross), the markings on the abdomen and on the sides, and the random pattern of the web.

While there are a few Orb Weaver spider species in my area, I know for a fact that this is not a young Orchard spider, because I have a photo of a young Orchard spider. Not only are the markings of the Orchard spider drastically different, but it's web has a circular pattenr. I also doubt that this is a young Spotted Orb Weaver, because once again, the Spotted Orb Weaver builds a web with a circular pattern, and the Spotted Orb Weaver sits much differently in its web as well.

So until I get clarification on the species, I am going to go with my hunch and say that this is a young Black & Yellow Argiope.

This was taken with the Canon MP-E at about 3-4x magnification. You can tell just how small this young spider is by looking at the small prey in its web: gnats and/or midges.