Apparently, damselfies are divided into two groups: pond damselflies and spreadwing damselflies. For the past ten years I've only encountered the pond variety, but last week I saw (and photographed) two spreadwing damselflies.
At rest, pond damselflies keep their wings parallel with their body; spreadwing damselflies have their wings pointed away from their body.
The first spreadwing was relatively easy to identify: the slender spreadwing damselfly (Lestes rectangularis), and it was one of the longer damselflies that I've seen.