wow, these are great shots! I worked doing dragonfly research for two summers...some of these are as good if not better than the pictures in field guides!
would you like a crash course in odonatology (the study of dragonflies and dragonflies)? too bad, you're getting one anyway!
the first two and bottom three are all damselflies. the third is a dragonfly. the obvious difference between the two groups is the size...dragonflies are, for the most part, larger. you can also tell the difference by the two pairs of wings. in dragonflies, the front pair differs in size/shape from the back pair; in damselflies they are nearly identical. (it's hard to see both pairs of wings in the damsels, since they rest with their wings all folded together and held upright). also, damselflies' eyes are situated on opposite sides of the head, while dragonflies' are on the top, and touch in the middle.
the top two are Calopteryx maculata (sorry, I don't know the common names!). fairly common, at least in reasonably clean water. their wings are so beautiful!
I'm not entirely certain on the identity of the dragonfly. it is in the genus Libellula.
the fourth, again, I'm not certain on. he (yes, it's a male) is in the genus Enallagma, which consists of several species that, in my opinion, all look exactly the same. the spot patterns on the abdomen tell the species, but I never learned how to distinguish them. it takes a trained eye and, in some cases, a microscope.
the last two are Nehalennia, which are some of my favorites. one of the first odonates I caught was a Nehalennia gracilis, which is what I think these are. it was very exciting, because it was a town record at a site where we weren't expecting to find it. its common name is the Sphagnum Sprite, and as it implies, N. gracilis lives by swamps with sphagnum. so, since we didn't know there was any sphagnum at the site, we didn't know to look for it!
Yesterday at work I had a damselfly very similar to the bottom 2 fly up and land on my fingure, it stayed there for a few minutes until I had to shake it away so I could get back to work.
It was more of a light brown color.