Off hand I've seen Eastern Pondhawks (males - blue like in my icon, females - green like the one in the photo), Elfin Skimmers, Red-mantled Saddlebags, 12-spotted Skimmers and what seemed to be a *very* blue Common Whitetail.

There are others, but I haven't gotten good enough shots of them yet to do a good match to a photo.

Those are the Illinois ones I know. I haven't checked on my Florida ones yet. (So behind in sorting photos)