Sneezeweed
Helenium puberulumAsteraceae
I walked right by these and then stopped in my tracks to take another look. It reminded me of a miniature, stunted sunflower. The yellow ray flowers were so tiny I initially thought something had chewed them off. I looked around some more and found several others looking just like this.
ps 05/28/10 - I originally posted this as unknown flower with a guess as to our native species. After looking some more, I'm fairly confident of this ID now, especially since it was growing next to standing water in an area of little disturbance.