The following were all taken at Blue Rock Pond, a small (approximately one acre, maybe less) impoundment near Lenhartsville, Pennsylvania. I was sorely tempted to post the photographs alone, but in the end decided to annotate after all. Feel free to ignore the text and just enjoy the pictures.
The rather similar blue dasher; note the brown-and-yellow striped thorax and the diffuse brown on the wings.
This one drove me crazy until I found it two days later in Sidney Dunkle's Dragonflies through Binoculars. It's a female eastern pondhawk, not depicted in the quick-reference foldout guide I had with me at the time.
Slaty skimmer. These were the most abundant and most cooperative of the odonates at the pond. I had originally identified them as great blue skimmers, but great blues have white faces.
This is a damselfly, not a dragonfly. I believe it's either a dancer or a bluet, but there are multiple (and very similar) species of both.
Several common green darners were present, but this is the best picture I could get; not once in three hours did I see any of them perch.
This last dragonfly was even less cooperative than the green darners. Only one individual visited the pond, just briefly, and like the green darners it never perched. This, the only picture I made, approaches the quality of purported photographs of Sasquatch or the Loch Ness monster—but if you embiggen and then zoom, you can just make out the wing markings that identify it as a twelve-spotted skimmer.