We have a plethora of Argiope spiders here lately.
I know this picture is a little blurry, but it shows the zig zag in the center of the web so well.
I talk to this girl every day, going in and out of the big henhouse. The pump is just to the right of the web, so every day I am careful to not bump the web as I raise and lower the pump.
These are the common black and yellow garden spiders, where you reach into the middle of a tomato plant and almost close your hand on the spider! Their bite will not hurt you. The females breed, and then kill their mates.
I think they are a beautiful spider. There are other webs in the enclosed porch of the big henhouse, Beau's old yard stall... but they are more common varieties. I actually have a photo somewhere of the duller male, dead in her clutches.
Here is a direct quote from Wikipedia (What on earth did we do before Wikipedia???):
"The white patterns are called stabilimentum and reflect UV light. They have been shown to play a role in attracting prey to the web, and possibly to prevent its destruction by large animals."
They are also the kind of web you can WALK RIGHT INTO if you are doing chores with your eyes almost closed in sleep at 6 in the morning!