http://imgur.com/a/Z99Z6 <--Photos of spider and web.

I'm growing yellow cherry tomatoes in a garden box. I've noticed for a few weeks now that there are a couple of webs under the plants, but until today I hadn't seen any residents. I am absolutely terrified of spiders, and my first instinct was to kill it, but I'm trying to think of the good karma and recent reduction in other insects eating the tomatoes. Can someone tell me what kind of spider I am dealing with? The first three photos are of the visible spider and her web, the last photo is of a similar web on the other side of the box. I live in Virginia Beach. I don't think the spider is more than an inch to inch-and-a-half from legtip to tip. Thanks in advance!