This is a female orb weaver (family: Araneidae) of some type, most likely in the genus of Neoscona. (Bugguide.net has had several spiders that look VERY similar to this, and have ID'd it to a genus, but not successfully to a specific species; sometimes a microscope is needed to confirm a species. Click Neoscona link and thumbnail below to see similar spiders...)



She is not harmful to people, but is very beneficial to your yard (loves to eat various insects). She spins a nice, ornate orb web between objects, and mostly likely is nocturnal. At dusk/night, she usually sits in the middle of the web, waiting for something to fly into her web. During the day, she may move off the web (or tear it down completely), and hide in a corner, or amongst some cover (like leaves), but it depends on location of the web, and the species... :)