Parasteatoda tepidariorum (Common House Spider).
Size: approx. 4 mm. Photo: 06/28/14, 5 pm.

Outside of the US, the Common House Spider is referred to as the American House Spider. They build tangled webs often in or near houses and feed on flies, mosquitoes, ants, wasps, etc. They have poor vision and usually retreat or pretend to be dead if threatened. The wikipedia link contains additional information on the typically harmless and rare bites.  
bug guide (this photo):